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1

Effect of solvents on radiation-induced ionic graft polymerization. [Gamma radiation  

SciTech Connect

The influence of various solvents on radiation-induced cationic (grafting of vinyl-n-butyl ether onto polyethylene) and anionic (grafting of 2-methyl-5-vinylpyridine onto polyethylene) graft polymerization was studied. This ionic grafting was performed in thoroughly dried systems at room temperature. It was established that electron-acceptor solvents promote cationic grafting but that electron-donor solvents promote the anionic. A clear correlation between the donor number of solvents and grafting value by the anionic mechanism was shown. There was no correlation between dielectric constants and grafting values. The reaction orders, according to monomer concentraton by 2-methyl-5-vinylpyridine grafting in various solvents, were equal to approximately 1.5 and 2 for the radical and anionic mechanisms, respectively. The effect of solvents on radiation-induced ionic graft polymerization is discussed. The results of this study indicate the correct choice of solvents for radiation-induced ionic grafting.

Kabanov, V.Ya.; Aliev, R.E.; Sidorova, L.P.

1980-03-01

2

Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane  

NASA Astrophysics Data System (ADS)

The structures of poly(methyl- n-propylsilane) (PMPrS) amphiphilically modified through ?-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of ?-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.

Tanaka, Hidenori; Iwasaki, Isao; Kunai, Yuichiro; Sato, Nobuhiro; Matsuyama, Tomochika

2011-08-01

3

Antimicrobial fabric adsorbed iodine produced by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Antimicrobial fabric was synthesized by radiation-induced graft polymerization of N-vinyl pyrrolidone onto polyolefine nonwoven fabric and subsequent adsorption of iodine. In response of the huge request for the antimicrobial material applied to face masks for swine flu in 2009, operation procedure of continuous radiation-induced graft polymerization apparatus was improved. The improved grafting production per week increased 3.8 times compared to the production by former operation procedure. Shipped antimicrobial fabric had reached 130,000 m2 from June until December, 2009.

Aoki, Shoji; Fujiwara, Kunio; Sugo, Takanobu; Suzuki, Koichi

2013-03-01

4

Radiation-Induced Graft Polymerization of Butadiene Gas onto Poly(Vinyl Chloride) in a Fluidized-Bed Reactor.  

National Technical Information Service (NTIS)

Radiation-induced graft polymerization of butadiene onto the powder of poly(vinyl chloride) has been studied in a fluidized bed. The apparent activation energy for the graft polymerization is 3.0 kcal/mol. The rate of grafting increases as the 0.6 power o...

H. Omichi K. Yoshida K. Araki K. Suzuki M. Gotoda

1976-01-01

5

Influence of relaxation transitions on radiation-initiated cationic graft polymerization. [Gamma radiation  

SciTech Connect

Radiation grafting of vinyl n-butyl ether (VBE) to polyvinyl chloride (PVC) over a broad temperature range was investigated. The relaxation transitions in the PVC/VBE system were also determined. Grafting of vinyl alkyl ethers proceeds entirely by a cationic mechanism in a reaction medium that has been dried to a water concentration no greater than 0.1-1.0 ppm. In this connection, the diffusion properties of water in the temperature region were studied. Commercial films of unplasticized PVC (thickness 200 M); were subjected to swelling in two systems: in a 50% solution of VBE in benzene at 25/sup 0/C, and in the pure monomer at 40/sup 0/C. The reaction mixtures were first dried over metallic sodium in a deaerated atmosphere. The specimens were irradiated in a Co gamma-radiation unit to a dose of 10 kGy at a dose rate of 3 Gy/sec. The first reaction mixture was investigated over a range of temperatures from -60/sup 0/ to +70/sup 0/C, and the second from -15/sup 0/ to +50/sup 0/C. The degree of grafting was determined from the increase in weight of the original ungrafted film. The temperature was held to within +/-1/sup 0/C. The relaxation transitions in the swollen polymer systems were determined by two methods, thermostimulated current (TSC) and thermomechanics (TM). It was found that in the region of the glass transition of a swollen PVC-VBE system, radiation-initiated cationic graft polymerization proceeds at a maximal rate, and there are changes in state of the water molecules (the agents of breaking the ion reaction chain) and in their diffusion properties within the matrix.

Kudryavtsev, V.N.; Kabanov, V.Ya.; Chalykh, A.E.; Spitsyn, V.I.

1982-05-01

6

Elucidation of dominant effect on initial bacterial adhesion onto polymer surfaces prepared by radiation-induced graft polymerization  

Microsoft Academic Search

Surface-modified polyethylene (PE) membrane sheets were prepared by the radiation-induced graft polymerization (RIGP) of an epoxy-group-containing monomer, glycidyl methacrylate (GMA). The epoxy ring of GMA was opened by introducing diethylamine (DEA) or sodium sulfite (SS). We examined the properties of these sheets by measuring the amount of grafting polymer, surface roughness and membrane potential, and also investigated the adhesion of

Akihiko Terada; Atsushi Yuasa; Satoshi Tsuneda; Akira Hirata; Akio Katakai; Masao Tamada

2005-01-01

7

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.

Kumari, Mamta; Gupta, Bhuvanesh; Ikram, Saiqa

2012-11-01

8

Graft polymerization of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid onto starch. [Gamma radiation  

Microsoft Academic Search

Mixtures of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (AASOâH) were graft polymerized onto starch by cobalt-60 irradiation, and the water absorbency and water solubility of the resulting products were determined. The conversion of monomers to polymer was nearly quantitative under simultaneous irradiation conditions. Products with high water absorbency were obtained with equal weights of starch and total monomers when acrylamide:AASOâH ratios ranged

G. F. Fanta; R. C. Burr; W. M. Doane

1979-01-01

9

The role of hydroperoxides as a precursor in the radiation-induced graft polymerization of methyl methacrylate to ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

A graft polymerization of methyl methacrylate (MMA) to ultra-high molecular weight polyethylene (UHMWPE) with Co-60 ?-ray irradiation in air at room temperature has been carried out. The grafting yields were measured as a function of the storage time (elapsed time from the end of irradiation to the start of grafting), and it was found that the yields reach at the maximum values at around several days since the end of irradiation. In order to clarify the precursor of the graft polymerization, changes of the radical yields and the carbonyl groups were measured as a function of storage time with ESR and microscopic FT-IR, respectively. From the similarities between the depth profiles of the hydroperoxide formation and the grafting products, it was concluded that the hydroperoxides can be main precursors of the grafting of the radiation-induced polymerization of MMA to UHMWPE under the given conditions.

Enomoto, Ichiro; Katsumura, Yosuke; Kudo, Hisaaki; Sekiguchi, Masayuki

2010-06-01

10

Advances in radiation grafting  

NASA Astrophysics Data System (ADS)

Graft copolymerization is an attractive means for modifying base polymers because grafting frequently results in the superposition of properties relating to the backbone and pendent chains. Among the various methods for initiating the grafting reaction, ionizing radiation is the cleanest and most versatile method of grafting available. Ion-exchange membranes play an important role in modern technology, especially in separation and purification of materials. The search for improved membrane composition has considered almost every available polymeric material because of its great practical importance. Grafting of polymers with a mixture of monomers is important since different types of chains containing different functional groups are included. A great deal is focused on the waste treatment of heavy and toxic metals from wastewater because of the severe problems of environmental pollution. Functionalized polymers suitable for metal adsorption with their reactive functional groups such as carboxylic and pyridine groups suitable for waste treatment were prepared by radiation grafting method. More reactive chelating groups were further introduced to the grafted copolymer through its functional groups by chemical treatments with suitable reagents. The advances of radiation grafting and possible uses are briefly discussed.

Hegazy, El-Sayed A.; AbdEl-Rehim, H. A.; Kamal, H.; Kandeel, K. A.

2001-12-01

11

Radiation-induced graft polymerization of maleic acid and maleic anhydride onto ultra-fine powdered styrene–butadiene rubber (UFSBR)  

Microsoft Academic Search

The functionalization of ultra-fine powdered styrene–butadiene rubber (UFSBR) was carried out using gamma radiation-induced graft polymerization of maleic acid (MA) and maleic anhydride (MAH), respectively. It was found that the graft yield of MA onto UFSBR increased rapidly up to the peak and then decreased with increasing MA content. Moreover, the peak shifted to the direction of lower MA content

Jing Peng; Haibing Xia; Maolin Zhai; Jiuqiang Li; Jinliang Qiao; Genshuan Wei

2007-01-01

12

Elucidation of dominant effect on initial bacterial adhesion onto polymer surfaces prepared by radiation-induced graft polymerization.  

PubMed

Surface-modified polyethylene (PE) membrane sheets were prepared by the radiation-induced graft polymerization (RIGP) of an epoxy-group-containing monomer, glycidyl methacrylate (GMA). The epoxy ring of GMA was opened by introducing diethylamine (DEA) or sodium sulfite (SS). We examined the properties of these sheets by measuring the amount of grafting polymer, surface roughness and membrane potential, and also investigated the adhesion of five Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas fluorescens and Paracoccus denitrificans, onto the prepared sheet surfaces. A linear relationship between the degree of grafting (dg) and surface roughness was observed. Moreover, membrane potential was dependent on the amount of DEA or SS as the ionizable group. These results indicate that RIGP enables the control of the physicochemical properties of such a sheet surface by adjusting dg and the subsequent conversion of functional groups. A batch test on bacterial adhesion onto the sheets clarified that the DEA-containing sheet (DEA sheet) exhibited an adhesion rate constant, k, significantly greater than those of other types of sheet. Clearly, the adhesion rate constant of the DEA sheet increased with dg, indicating that electrostatic interaction is the most decisive factor for bacterial adhesion when it works as an attractive force. Furthermore, the densities of bacteria adhering onto the GMA-containing sheet (GMA sheet) and the SS-containing sheet (SS sheet) were almost the same as that onto a PE sheet, whereas that onto a DEA sheet significantly increased. Thus, the introduction of the GMA- and SS-containing graft chain did not have much influence on bacterial adhesion onto the surfaces, supporting the conclusion that the promotion of bacterial adhesion onto the GMA and SS sheets was due to an increase in surface area resulting from RIGP. Moreover, the scanning electron microscopy images of the sheet surfaces indicate that the conditions and morphologies of initial bacterial adhesion are dependent on surface properties, particularly membrane potential. PMID:15922579

Terada, Akihiko; Yuasa, Atsushi; Tsuneda, Satoshi; Hirata, Akira; Katakai, Akio; Tamada, Masao

2005-06-25

13

Radiation-Induced Grafting on Polyamides.  

National Technical Information Service (NTIS)

Earlier work indicated that in the radiation-induced grafting of vinyl monomers on polymeric films, the plasticity of the film being grafted is determined by the Hildebrand solubility parameter of the grafting solution. In the grafting of styrene on nylon...

J. E. Wilson

1973-01-01

14

Graft polymerization of vinyl acetate onto silica  

Microsoft Academic Search

The free-radical graft polymerization of vi- nyl acetate onto nonporous silica particles was studied ex- perimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free-rad- ical graft polymerization of vinyl acetate in ethyl acetate with 2,2-azobis(2,4-dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by vol- ume and the reaction was spanned from 50 to

Van Nguyen; Wayne Yoshida; Yoram Cohen

2003-01-01

15

Electron-beam induced RAFT-graft polymerization of poly(acrylic acid) onto PVDF  

NASA Astrophysics Data System (ADS)

This paper explores for the first time the post-radiation-induced-graft polymerization on solid substrate using reversible addition-fragmentation transfer (RAFT) mechanism. Radiation-induced graft polymerization onto polymers is a potentially interesting technique to create easily new materials from highly resistant polymers, e.g. surface graft polymerization of acrylic acid (AA) onto poly(vinylidene difluoride) (PVDF) improves its surface properties without losing its excellent mechanical properties. As a consequence of the radical nature of the polymerization processes it is difficult to control molecular weight of grafted chains, and therefore design and standardize the properties of the final product. RAFT polymerization is a suitable method to obtain monodisperse polymers. The ability of the RAFT agents to control the polymer chain length could be an interesting approach to improve the grafted polymers obtained by post-radiation-induced-graft polymerization technique. In this way, graft polymerization of AA onto electron-beam irradiated ?-PVDF was performed using trithiocarbonic acid bis(1-phenylethyl) ester as a RAFT agent to control the radical polymerization. We studied several grafting parameters such as solvent, monomer concentration and grafting time in order to achieve a poly(acrylic acid) (PAA) layer onto PVDF surface. Acetic acid was found to be the best solvent for many reasons, as to drive graft polymerization mainly to the polymer surface, complete solubility and stability of all reactants. Hydrolysis of PAA chains was also studied in order to remove the trithiocarbonate functionality from the grafted polymer. A mild chemical condition was achieved in order to have thiol groups that were detected onto the modified PVDF by specific enzymatic reaction.

Grasselli, M.; Betz, N.

2005-07-01

16

High fluence irradiation effect on the ion beam graft polymerization method  

NASA Astrophysics Data System (ADS)

Radiation graft polymerization method has been applied to make many industrial product. Ion beam graft polymerization method has been developed by Betz and many researchers, and we have also developed the method with proton whose energy is below a few MeV. Using the method, the substrate, e.g. polyethylene film, is graft-polymerized and has the graft chains near the surface. To conduct the method for some times, the structure of graft chains near the surface can be formed. When we want to produce the graft chains inside of the substrate, the graft chains near the surface are unnecessary. One of our objectives is to produce a functional polymer with a structure in the film. When the sample is irradiated in sufficiently high fluence, the sample can't be graft-polymerized in the next irradiation. Comparing the density of radicals and the number of double bond with the degree of grafting, the reason why formation of a part not grafted in high fluence irradiation was discussed. Because the number of the double bond and the allyl radicals in PE are increased for high fluence irradiation, the number of the alkyl radical as a grafting point is decreased. Moreover, the alkyl radical is not produced in following irradiation since existence of double bond and peroxy radical.

Taniike, Akira; Hirooka, Yuya; Nakanishi, Noriaki; Nakamura, Raito; Furuyama, Yuichi

2014-07-01

17

Obtencion de membranas polimericas cationicas por el metodo de injerto por radiacion. (Obtention of cationic polymeric membranes by radiation-induced grafting method).  

National Technical Information Service (NTIS)

Radiation-induced grafting of LDPE with the monomers, acrylic acid and methacrylic acid, has been studied. The grafting was made with several presentations of LDPE (foil, powder and pellets) by direct method using a Co(sup 60) gamma rays. The irradiation ...

H. Marin H E

1994-01-01

18

A study of the kinetics of radiational graft polymerization of acrylic monomers on a butadiene-styrene thermoelastomer  

SciTech Connect

The present work was a study of the kinetics of nonstationary radiational copolymerization of acrylonitrile (AN) and acrylic acid (AA) on a butadiene-styrene thermoelastomer (TE) and block-copolymers.

Timofeeva, V.F.; Ryabchikova, G.G.; Pikaev, A.K.; Spitsyn, V.I.

1982-10-20

19

Graft polymerization of native chicken feathers for thermoplastic applications.  

PubMed

Inexpensive and biodegradable thermoplastics were developed through graft polymerization of native chicken feather with methyl acrylate as a potential substitute for petroleum products. Poultry feathers are available in large quantities at a low price. However, natural chicken feathers have poor thermoplasticity, cannot be used to develop thermoplastic products, have very limited industrial applications, and are often considered as solid wastes. In this research, the effects of graft polymerization conditions, such as molar ratio of NaHSO(3) to K(2)S(2)O(8), initiator and monomer concentrations, pH, temperature and time of polymerization, on grafting parameters, that is, the conversion of monomer to polymer, grafting percentage, and grafting efficiency were evaluated. Methyl acrylate was found to be successfully grafted onto functional groups on the surfaces of the chicken feathers, and optimal graft polymerization conditions were also obtained. The feather-g-poly(methyl acrylate) developed showed good thermoplasticity, and feather films had substantially higher tensile properties than soy protein isolate and starch acetate films. PMID:21302951

Jin, Enqi; Reddy, Narendra; Zhu, Zhifeng; Yang, Yiqi

2011-03-01

20

Corona-induced graft polymerization for surface modification of porous polyethersulfone membranes  

Microsoft Academic Search

Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed

Li-Ping Zhu; Bao-Ku Zhu; Li Xu; Yong-Xiang Feng; Fu Liu; You-Yi Xu

2007-01-01

21

Crosslinked grafted PVC obtained by direct radiation grafting  

NASA Astrophysics Data System (ADS)

Direct radition-induced grafting of 4-vinylpyridine onto both pure and plasticized poly(vinyl chloride) has been studied. The effect of grafting conditions such as solvent, monomer concentration, irradiation dose, and inhibitor concentration on the grafting yield was investigated. The grafting process was enhanced by using distilled water as diluent and higher degrees of grafting were obtained as compared with other solvents used (benzene, methanol, and a mixture of methanol and water). The homopolymerization of 4-vinylpyridine was reduced to a minimum using ammonium ferrous sulfate and the suitable optimum concentration of the inhibitor was found to be 0.25 wt %. It was observed that the degrees of grafting onto plasticized PVC were higher than those onto pure one, at constant grafting conditions. The diffusibility of the monomer solution through the trunk polymers enhanced at higher monomer concentrations. The higher the monomer concentration the higher the degrees of grafting obtained. The dependence of the grafting rate on monomer concentration was found to be 0.15 and 0.4 order for the grafting onto pure and plasticized PVC films, respectively. The degree of grafting, at the higher irradiation doses, deviated from linearity and it tends to level off due to the recombination of some of the free radicals without initiating graft polymerization. Gel determination in the grafted films was investigated. The gel content in both grafted extracted pure and plasticized PVC films increased with the degree of grafting to reach a certain limiting values.

Hegazy, El-Sayed A.; Dessouki, Ahmed M.; El-Dessouky, Maher M.; El-Sawy, Naeem M.

22

Application of radiation-graft material for metal adsorbent and crosslinked natural polymer for healthcare product  

Microsoft Academic Search

Graft polymerization and crosslinking in radiation processing are attractive techniques for modification of the chemical and physical properties of conventional polymers. The graft polymerization and subsequent chemical treatment can introduce a chelate agent function into a conventional polymer such as polyethylene. The obtained amidoxime fibrous adsorbent was applied to the recovery of uranium from seawater. Soaking of 350kg adsorbent 12

Masao Tamada; Noriaki Seko; Fumio Yoshii

2004-01-01

23

Graft polymerization of vinyl acetate onto starch. Saponification to starch-g-poly(vinyl alcohol). [. gamma. rays  

Microsoft Academic Search

Graft polymerizations of vinyl acetate onto granular cornstarch were initiated by cobalt-60 irradiation of starch-monomer-water mixtures, and ungrafted poly(vinyl acetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. Over half of the polymer was present as ungrafted poly(vinyl acetate) (grafting efficiency less than 50%), and

G. F. Fanta; R. C. Burr; W. M. Doane; C. R. Russell

1979-01-01

24

Gamma radiation grafted polymers for immobilization of Brucella antigen in diagnostic test studies  

NASA Astrophysics Data System (ADS)

The radiation grafting process has a wide field of industrial applications, and in the recent years the immobilization of biocomponents in grafted polymeric materials obtained by means of ionizing radiations is a new and important contribution to biotechnology. In the present work, gamma preirradiation grafting method was employed to produce acrylics hydrogels onto polyethylene (PE), polyvinyl chloride (PVC) and polystyrene (PS). Two monomers were used to graft the previously mentioned polymers: methacrylic acid (MAAc) and acrylamide (AAm), and several working conditions were considered as influencing the degree of grafting. All this grafted polymers were used to study the possibility of a subsequent immobilization of Brucella antigen (BAg) in diagnostic test studies (ELISA).

Docters, E. H.; Smolko, E. E.; Suarez, C. E.

25

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization.  

PubMed

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H2 and O2 plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37°C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant. PMID:25063140

Abednejad, Atiye Sadat; Amoabediny, Ghasem; Ghaee, Azadeh

2014-09-01

26

Durable Nanolayer Graft Polymerization of Functional Finishes Using Atmospheric Plasma  

NASA Astrophysics Data System (ADS)

Various applications of atmospheric pressure plasma were investigated in conjunction with different chemistries on nonwoven materials including spunbond polyester (PET) and spunbod polypropylene for fuel separation and antimicrobial functionalities. Hydrophobic/Oleophobic properties were conferred on nonwoven polyester (PET) via plasma-induced graft polymerization of different hydrophobic non-C8 perfluorocarbon chemistry including perfluorohexylethylmethacrylate, perfluorohexylethylacrylate, allylpentafluorobenzene, pentafluorostyrene, or 1,3-divinyltetramethyldisiloxane in the vapor form using both in-situ and down-stream plasma configurations. Different nanolayers of the grafted polymer were furnished on nonwovens to generate surfaces with different level of wettabilities for medical applications and water/fuel separation. The effect of various hydrophobic chemistry, different plasma conditions, and plasma device parameters including plasma power and plasma exposure time were studied and the performance was characterized by measuring the contact angle and the wettability rating against liquids with broad range of surface tensions. Vapor deposition of 2-(perfluorohexyl)ethyl methacrylate and pentafluorostyrene on nonwoven PET followed by plasma-induced graft polymerization was investigated for possible use in water/fuel separation. Different nanolayer thicknesses (80-180nm) of the grafted polymer were achieved to generate surfaces with different wettabilities for water/fuel separation of different fuel compositions. The effect of different plasma conditions and device parameters including the flow rate of monomers, power of the device, and time of plasma exposure on the separation of different fuels was studied and characterized by measuring the surface energy of the treated substrates. The surface chemistry and morphology of the treated samples were characterized using XPS, SEM and TOF-SIMS techniques which confirmed the grafting of monomer onto the substrate. Furthermore, spunbond nonwoven polypropylene fabric, commonly used for hygienic products, was treated with diallyldimethylammonium chloride (DADMAC). Atmospheric pressure glow discharge plasma was used to induce free radical chain polymerization of the ADMAC monomer, which conferred a graft polymerized network on the fabric with durable antimicrobial properties. The effect of different DADMAC concentration, and plasma conditions including the RF power and the time of plasma exposure were studied and the optimum treatment conditions were identified by calculating the surface charge density on the treated fabrics. The presence of poly-DADMAC on the polypropylene surface was confirmed using SEM, FT-IR and TOF-SIMS. Antibacterial performance was investigated using standard test methods (AATCC TM 100) for both gram positive and gram negative bacteria. The antimicrobial results showed 6 log reductions in the bacterial activities of K. pneumoniae and S .aureus, which was unprecedented using a plasma-induced graft polymerization approach.

Mazloumpour, Maryam

27

Grafting polystyrene onto silica nanoparticles via RAFT polymerization  

Microsoft Academic Search

Reversible addition–fragmentation chain transfer (RAFT) polymerization was used to graft polystyrene (PS) onto silica nanoparticles. A novel route was used to prepare the RAFT agent, 2-butyric acid dithiobenzoate (BDB) by substitution of dithiobenzoate magnesium bromide with sodium 2-bromobutyrate under alkali condition in aqueous solution. Epoxy groups were covalently attached to silica nanoparticles by condensation reaction of 3-glycidyloxypropyltrimethoxysilane (GPS) with the

Chun-Hua Liu; Cai-Yuan Pan

2007-01-01

28

Solvent effects on the synthesis of ion-exchange membranes by radiation-induced graft polymerization of methyl. cap alpha. ,. beta. ,. beta. -trifluoroacrylate. [Freon 113  

SciTech Connect

Methyl ..cap alpha..,..beta..,..beta..-trifluoroacrylate (MTFA) was grafted onto polyethylene (PE) film and fluorine-containing films to make ion-exchange membranes. In the case of PE the grafting yield was not influenced by the presence of trifluorotrichloroethane (Freon 113) in the reaction mixture, while the presence of methanol decreased the grafting yield. The transversal distribution of graft chains in the film observed by electron-probe x-ray microanalysis showed that when the grafting was carried out in the presence of Freon the amount of graft chains in the central part of PE film was much larger than that at the film surface and that the grafts obtained in the absence of Freon were located mainly at the film surface. The electric resistance of the graft PE film obtained in the presence of Freon decreased more than that of the one obtained in the absence of Freon. The weight loss of the graft films in H/sub 2/O/sub 2/ solution was negligibly small.

Omichi, H.; Okamoto, J.

1982-06-01

29

Graft Polymerization of Acrylic Acid on a Polytetrafluoroethylene Panel by an Inductively Coupled Plasma  

Microsoft Academic Search

Surface modification on a polytetrafluoroethylene (PTFE) panel was performed with sequential nitrogen plasma treatments and surface-initiated polymerization. By introducing COO- groups to the surface of the PTFE panel through grafting polymerization of acrylic acid (AA), a transparent poly (acrylic acid) (PAA) membrane was achieved from acrylic acid solution. Grafting polymerization initiating from the active groups was achieved on the PTFE

Yan Lan; Qingliang You; Cheng Cheng; Suzhen Zhang; Guohua Ni; M. Nagatsu; Yuedong Meng

2011-01-01

30

Biodegradable metal adsorbent synthesized by graft polymerization onto nonwoven cotton fabric  

NASA Astrophysics Data System (ADS)

A fibrous adsorbent for Hg ions was synthesized by radiation-induced emulsion graft polymerization of glycidyl methacrylate (GMA) onto a nonwoven cotton fabric and subsequent chemical modification. The optimal pre-irradiation dose for initiation of the graft polymerization of GMA, which minimized the effects of radiation damage on the mechanical strength of the nonwoven cotton fabric, was found to be 10 kGy. The GMA-grafted nonwoven cotton fabric was subsequently modified with ethylenediamine (EDA) or diethylenetriamine (DETA) to obtain a Hg adsorbent. The resulting amine-type adsorbents were evaluated for batch and continuous adsorption of Hg. In batch adsorption, the distribution coefficients of Hg reached 1.9×10 5 and 1.0×10 5 for EDA- and DETA-type adsorbents, respectively. A column packed with EDA-type adsorbent removed Hg from 1.8 ppm Hg solution at a space velocity of 100 h -1, which corresponds to 16,000 times the volume of the packed adsorbent. The adsorbed Hg on the EDA-type adsorbent could be completely eluted by 1 M HCl solution. A microbial oxidative degradation test revealed that the EDA-type adsorbent is biodegradable.

Sekine, Ayako; Seko, Noriaki; Tamada, Masao; Suzuki, Yoshio

2010-01-01

31

Polymer brush gradients grafted from plasma-polymerized surfaces.  

PubMed

A new method for generating a surface density gradient of polymer chains is presented. A substrate-independent polymer deposition technique was used to coat materials with a chemical gradient based on plasma copolymerization of 1,7-octadiene and allylamine. This provided a uniform chemical gradient to which initiators for atom transfer radical polymerization (ATRP) were immobilized. After surface-initiated atom transfer radical polymerization (SI-ATRP), poly(2-hydroxyethyl methacrylate) (PHEMA) chains were grafted from the surface and the measured thickness profiles provided direct evidence for how surface crowding provides an entropic driving force resulting in chain extension away from the surface. Film thicknesses were found to increase with the position along the gradient surface, reflecting the gradual transition from collapsed to more extended surface-tethered polymer chains as the grafting density increased. The method described is novel in that the approach provides covalent linkages from the polymer coating to the substrate and is not limited to a particular surface chemistry of the starting material. PMID:24967529

Coad, Bryan R; Bilgic, Tugba; Klok, Harm-Anton

2014-07-22

32

Radiation effects on polymeric materials  

NASA Technical Reports Server (NTRS)

It is important to study changes in properties of polymeres after irradiation with charged particles, with ultraviolet radiation, and with combinations of both. An apparatus for this purpose has been built at the NASA Langley Research Center. It consists of a chamber 9 inches in diameter and 9 inches high with a port for an electron gun, another port for a mass spectrometer, and a quartz window through which an ultraviolet lamp can be focused. The chamber, including the electron gun and the mass spectrometer, can be evacuated to a pressure of 10 to the 8th power torr. A sample placed in the chamber can be irradiated with electrons and ultraviolet radiation separately, sequentially, or simultaneously, while volatile products can be monitored during all irradiations with the mass spectrometer. The apparatus described above has been used to study three different polymer films: lexan; a polycarbonate; P1700, a polysulfone; and mylar, a polyethylene terephthalate. All three polymers had been studied extensively with both electrons and ultraviolet radiation separately, but not simultaneously. Also, volatile products had not been monitored during irradiation for the materials. A high electron dose rate of 530 Mrads/hr was used so that a sufficient concentration of volatile products would be formed to yield a reasonable mass spectrum.

Kiefer, Richard L.

1988-01-01

33

Surface modification of polypropylene microfiltration membranes by graft polymerization of N-vinyl-2-pyrrolidone  

Microsoft Academic Search

A hydrophilic polymer, poly(N-vinyl-2-pyrrolidone), was tethered on the surface of polypropylene microfiltration membrane (PPMM) by UV photo-assisted and ?-ray pre-irradiation induced graft polymerizations. Results revealed that the ?-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. The chemical changes of the membrane surface were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Pure water

Zhen-Mei Liu; Zhi-Kang Xu; Jian-Qin Wang; Jian Wu; Jun-Jie Fu

2004-01-01

34

Studies on the graft polymerizations of styrene and methyl methacrylate to hydroxyl terminated polybutadiene  

Microsoft Academic Search

Hydroxyl terminated Polybutadiene (HTPB) was grafted with styrene (St) or methyl methacrylate (MMA) by free radical solution polymerization. The graft copolymerizations were conducted in benzene at 70 °C. The initiators used were benzoyl peroxide (BPO) and azobis-isobutyronitrile (AIBN). The microstructures of theobtained graft copolymers were characterized by13C NMR measurement and the DEPT technique, as well as by IR spectrometer. The

Chang-Tay Lin; Mon-Chun Liu

1995-01-01

35

Radiation-Induced Grafting on Polyamides.  

National Technical Information Service (NTIS)

The objective of the project was to investigate radiation-induced grafting on polyamides, with emphasis on fluorine-containg vinyl monomers. The principal experimental technique was the gamma ray irradiation of polyamide film samples immersed in suitable ...

J. E. Wilson

1972-01-01

36

Radiation grafting on natural films  

NASA Astrophysics Data System (ADS)

Different methods of polymer grafting using gamma irradiation are reported in the present study for the preparation of newly functionalized biodegradable films, and some important properties related to their mechanical and barrier properties are described. Biodegradable films composed of zein and poly(vinyl alcohol) (PVA) were gamma-irradiated in presence of different ratios of acrylic acid (AAc) monomer for compatibilization purpose. Resulting grafted films (zein/PVA-g-AAc) had their puncture strength (PS=37-40 N mm-1) and puncture deformation (PD=6.5-9.8 mm) improved for 30% and 50% PVA in blend, with 5% AAc under 20 kGy. Methylcellulose (MC)-based films were irradiated in the presence of 2-hydroxyethyl methacrylate (HEMA) or silane, in order to determine the effect of monomer grafting on the mechanical properties of films. It was found that grafted films (MC-g-HEMA and MC-g-silane) using 35% monomer performed higher mechanical properties with PS values of 282-296 N mm-1 and PD of 5.0-5.5 mm under 10 kGy. Compatibilized polycaprolactone (PCL)/chitosan composites were developed via grafting silane in chitosan films. Resulting trilayer grafted composite film (PCL/chitosan-g-silane/PCL) presented superior tensile strength (TS=22 MPa) via possible improvement of interfacial adhesion (PCL/chitosan) when using 25% silane under 10 kGy. Finally, MC-based films containing crystalline nanocellulose (CNC) as a filling agent were prepared and irradiated in presence of trimethylolpropane trimethacrylate (TMPTMA) as a grafted plasticizer. Grafted films (MC-g-TMPTMA) presented superior mechanical properties with a TS of 47.9 MPa and a tensile modulus (TM) of 1792 MPa, possibly due to high yield formation of radicals to promote TMPTMA grafting during irradiation. The addition of CNC led to an additional improvement of the barrier properties, with a significant 25% reduction of water vapor permeability (WVP) of grafted films.

Lacroix, M.; Khan, R.; Senna, M.; Sharmin, N.; Salmieri, S.; Safrany, A.

2014-01-01

37

Radiation formation of polymeric nanogels  

Microsoft Academic Search

An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be

P. Ulanski; I. Janik; J. M. Rosiak

1998-01-01

38

Multifunctional silk fabrics by means of the plasma induced graft polymerization (PIGP) process  

Microsoft Academic Search

An argon plasma induced graft polymerization (PIGP) process has been used to impart durable flame retardancy to silk fabrics. Phosphate and phosphoramidate monomers are known to be especially effective as flame retardants and have been used in this work for this application. Furthermore, water repellent finishing on silk fabrics could be achieved by means of SF6 plasma treatment. The grafting

Kanchit Kamlangkla; Satreerat K. Hodak; Joëlle Levalois-Grützmacher

2011-01-01

39

Cationic resins prepared by radiation-induced graft copolymerization  

NASA Astrophysics Data System (ADS)

Poly(acrylamide-acrylic acid) resin P(PAM-AA) was prepared by gamma radiation-initiated grafting copolymerization of acrylic acid (AA) on polyacrylamide (PAM) by addition of Mohr's salt as an inhibitor for homopolymerization. The polymerization was studied at different absorbed doses, polymor/monomer ratios and the monomer concentrations. The grafting percentage increases by increasing the dose and the monomer concentration and decreases by increasing polymer/monomer ratio. There is no significant change in the swelling degree of the obtained resin. It was found that the capacity of the resins towards Cu 2+ increases with increasing the monomer concentration and decreases by increasing the polymer/monomer ratio. The capacity of the resin was found to be constant at all doses.

Siyam, T.; Youssef, H. A.

1999-07-01

40

Synthesis of amphiphilic polycyclooctene-graft–poly(ethylene glycol) copolymers by ring-opening metathesis polymerization  

Microsoft Academic Search

In this paper, a novel monomer of 4-methyl-3-(carbamate)–carbanilic acid-4-cyclooctene ester (MCCCE) was synthesized and characterized by FTIR, NMR and ESI-MS. Polycyclooctene-graft-blocked isocyanate copolymers were prepared by the copolymerization of MCCCE and cyclooctene via ring-opening metathesis polymerization (ROMP). Amphiphilic polycyclooctene-graft–PEG copolymers were prepared by melt mixing the polycyclooctene-graft-blocked isocyanate copolymers with poly(ethylene glycol) (PEG) at 200°C. The blocked isocyanate group on

Hengchong Shi; Dean Shi; Ligang Yin; Shifang Luan; Jie Zhao; Jinghua Yin

2010-01-01

41

Radiation induced graft copolymerization of methyl methacrylate onto chrome-tanned pig skins  

NASA Astrophysics Data System (ADS)

Graft copolymerization of methyl methacrylate (MMA) onto chrome-tanned pig skins was carried out by the irradiation with 60Co ?-rays. The grafted polymethyl methacrylate (PMMA) chains were isolated by acid hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the isolated grafts by reaction with ninhydrin. The grafting yield of MMA in aqueous emulsion was found to be higher than that for pure MMA and MMA in acetone. The degree of grafting increases with increasing monomer concentration in emulsion and reaches maximum at radiation dose ca 15 kGy. The yield of grafting is very high - ca 90% of monomer converts into copolymer and only 10% is converted into homopolymer. The present paper reports the physical properties of chrome-tanned pig skins after graft polymerization with MMA in emulsion. Modified leathers are more resistant against water absorption and abrasion in comparison with unmodified ones. They have more uniform structure over the whole surface, greater thickness and stiffness. The results reported seem to indicate that MMA may be used in the production of shoe upper and sole leathers. The mechanism of some of the processes occuring during radiation grafting of MMA in water emulsion on tanned leathers has been also suggested and discussed.

Pietrucha, K.; P?kala, W.; Kroh, J.

42

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization  

PubMed Central

Summary We describe the use of one of the most advanced radical polymerization techniques, the reversible addition fragmentation chain transfer (RAFT) process, to produce highly functional core–shell particles based on a silica core and a shell made of functional polymeric chains with very well controlled structure. The versatility of RAFT polymerization is illustrated by the control of the polymerization of vinylbenzyl chloride (VBC), a highly functional monomer, with the aim of designing silica core–poly(VBC) shell nanoparticles. Optimal conditions for the control of VBC polymerization by RAFT are first established, followed by the use of the “grafting from” method to yield polymeric brushes that form a well-defined shell surrounding the silica core. We obtain particles that are monodisperse in size, and we demonstrate that the exceptional control over their dimensions is achieved by careful tailoring the conditions of the radical polymerization.

Moraes, John; Ohno, Kohji; Gody, Guillaume; Maschmeyer, Thomas

2013-01-01

43

Preparation of ion exchange membranes by radiation grafting of acrylic acid on FEP films  

NASA Astrophysics Data System (ADS)

Ion exchange membranes were prepared by radiation induced graft polymerization of acrylic acid on FEP films using preirradiation method. The influence of the ferrous sulfate and monomer concentration on the degree of grafting was investigated. Divinylbenzene, tetraethyleneglycol dimethacrylate and methylene bisacrylamide were used as crosslinkers. The membranes were characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction analysis. The swelling bahavior and specific resistivity of membranes as function of the degree of grafting and crosslink nature were evaluated. These crosslinkers had influence on the swelling and the specific resistivity of membranes depending on their chemical nature.

Gupta, Bhuvanesh; Muzyyan, Nusrat; Saxena, Shalini; Grover, Navdeep; Alam, Sarwar

2008-01-01

44

A versatile, fast, and efficient method of visible-light-induced surface grafting polymerization.  

PubMed

To overcome the problem caused by the lability of the Au-S bond, we demonstrate the first use of Mn2(CO)10 for visible-light-induced surface grafting polymerization on Au surfaces in this paper. The visible-light-induced surface grafting of poly(N-isopropylacrylamide) (PNIPAAm) has the features of a "controlled" polymerization, which is characterized by a linear relationship between the thickness of the grafting layer and the monomer concentration. Ellipsometry indicated the formation of PNIPAAm films of up to ?200 nm in thickness after only 10 min of polymerization at room temperature, demonstrating that this is a very fast process in comparison with traditional grafting polymerization techniques. Moreover, to demonstrate the potential applications of our approach, different substrates grafted by PNIPAAm and the covalent immobilization of a range of polymers on Au surfaces were also demonstrated. Considering the advantages of simplicity, efficiency, and mild reaction conditions as well as the ability of catecholic derivatives to bind to a large variety of substrates, this visible-light-induced grafting method is expected to be useful in designing functional interfaces. PMID:24749896

Xiong, Xinhong; Liu, Wei; Luan, Yafei; Du, Jun; Wu, Zhaoqiang; Chen, Hong

2014-05-20

45

Antibacterial activity of polymeric substrate with surface grafted viologen moieties  

Microsoft Academic Search

An asymmetric viologen, N-hexyl-N?-(4-vinylbenzyl)-4,4?-bipyridinium bromide chloride (HVV), was synthesized and graft copolymerized with commercial PET films. The surface graft concentration of HVV on the PET film is easily controlled by varying the monomer concentration used in the UV-induced graft copolymerization process. The HVV surface functionalized PET film functions as a smart window whose transmittance is reduced upon exposure to light.

Zhilong Shi; K. G Neoh; E. T Kang

2005-01-01

46

Radiation sterilization of polymeric implant materials  

SciTech Connect

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and/or blood, may adversely affect their long-term mechanical and/or biological performance (tissue and/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

Bruck, S.D.; Mueller, E.P.

1988-08-01

47

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.  

PubMed

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure. PMID:20644821

Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

2010-03-01

48

Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization  

SciTech Connect

Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

1988-01-01

49

Synthesis and characterization of polymeric linseed oil grafted methyl methacrylate or styrene.  

PubMed

Syntheses of wholly natural polymeric linseed oil (PLO) containing peroxide groups have been reported. Peroxidation, epoxidation and/or perepoxidation reactions of linseed oil, either under air or under oxygen flow at room temperature, resulted in polymeric peroxides, PLO-air and PLO-ofl, containing 1.3 and 3.5 wt.-% of peroxide, with molecular weights of 2 100 and 3 780 Da, respectively. PLO-air contained cross-linked film up to 46.1 wt.-% after a reaction time of 60 d, associated with a waxy, soluble part (PLO-air-s) that was isolated with chloroform extraction. PLO-ofl was obtained as a waxy, viscous liquid without any cross-linked part at the end of 24 d under visible irradiation and oxygen flow. Polymeric peroxides, PLO-air-s and PLO-ofl initiated the free radical polymerization of both methyl methacrylate (MMA) and styrene (S) to give PMMA-graft-PLO and PS-graft-PLO graft copolymers in high yields with Mw varying from 37 to 470 kDa. The polymers obtained were characterized by FT-IR, (1)H NMR, TGA, DSC and GPC techniques. Cross-linked polymers were also studied by means of swelling measurements. PMMA-graft-PLO graft copolymer film samples were also used in cell-culture studies. Fibroblast cells were well adhered and proliferated on the copolymer film surfaces, which is important in tissue engineering. PMID:15468258

Cakmakli, Birten; Hazer, Baki; Tekin, Ishak Ozel; Kizgut, Sait; Koksal, Murat; Menceloglu, Yusuf

2004-07-14

50

Morphological control of PEMFC electrode by graft polymerization of polymer electrolyte onto platinum-supported carbon black  

Microsoft Academic Search

An increase in platinum catalyst utilization in polymer electrolyte fuel cells is necessary to improve performance and reduce costs. In the present study, a novel electrode preparation method was developed, based on the process of graft polymerization of electrolyte polymer onto a carbon black support. In this method, the electrolyte polymer is graft polymerized from monomer solution, which is able

Hirotaka Mizuhata; Shin-ichi Nakao; Takeo Yamaguchi

2004-01-01

51

Antifouling microfiltration membranes prepared from acrylic acid or methacrylic acid grafted poly(vinylidene fluoride) powder synthesized via pre-irradiation induced graft polymerization  

Microsoft Academic Search

This study describes the manufacture, characterization and evaluation of microfiltration membranes with antifouling properties. Poly(vinylidene fluoride) (PVDF) powder was grafted with acrylic acid (AAc) or methacrylic acid (MAA) via a pre-irradiation induced graft polymerization technique. The presence of graft chains was proven by FT-IR spectroscopy. Then, microfiltration (MF) membranes were cast from AAc or MAA grafted PVDF powder with different

Bo Deng; Ming Yu; Xuanxuan Yang; Bowu Zhang; Linfan Li; Leidong Xie; Jingye Li; Xiaofeng Lu

2010-01-01

52

Modification of Synthetic Fibers by Radiation-Induced Grafting.  

National Technical Information Service (NTIS)

The present report describes studies to modify properties of synthetic fibers by radiation-induced grafting technique. This technique was employed since it is considered to be generally applicable to the grafting of a radically polymerizable monomer onto ...

K. Kaji

1981-01-01

53

Corona-induced graft polymerization for surface modification of porous polyethersulfone membranes  

NASA Astrophysics Data System (ADS)

Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis. Porosimetry measurements indicate the average pore diameters and porosities of the modified membranes decrease with the increase of the GY. The hydrophilicity and surface wetting properties of the original and modified membranes were evaluated by observing the dynamic changes of water contact angles. It is found that the grafting of AA occurs not only on the membrane surfaces, but also on the pore walls of the cells inside the membrane. The permeability experiments of protein solution reveal that the grafting of PAA endows the modified membranes with enhanced fluxes and anti-fouling properties. The optimized GY of AA is in the range of 150-200 ?g/cm 2. In addition, the tensile experiments show the corona discharge treatment with the power lower than 150 W yields little damage to the mechanical strength of the membranes.

Zhu, Li-Ping; Zhu, Bao-Ku; Xu, Li; Feng, Yong-Xiang; Liu, Fu; Xu, You-Yi

2007-05-01

54

Technique of radiation polymerization in fine art conservation: a potentially new method of restoration and preservation. [Uv and electron beams  

SciTech Connect

The technique of using radiation polymerization for the restoration and preservation of art treasures is considered. The processes discussed include both radiation grafting and rapid cure procedures, particularly reactions initiated by uv and eb. Representative examples where the technique has already been used are treated including typical applications with paintings, tapestries, leather and archival repair. The structure of the monomers and oligomers used in both grafting and rapid cure systems is outlined. The experimental conditions where grafting may occur during radiation rapid cure processing are discussed. Possible future developments of the technique are outlined. 1 figure, 8 tables.

Garnett, J.L. (Univ. of New South Wales, Kensington, Australia); Major, G.

1982-01-01

55

Vinyl acetate polymerization by ionizing radiation  

Microsoft Academic Search

For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. >From the characterization

A. C. Mesquita; M. N. Mori; J. M. Vieira; L. G. Andrade e. Silva

2002-01-01

56

Vinyl acetate polymerization by ionizing radiation  

Microsoft Academic Search

For this work an irradiation system to be used in the polymerization of the vinyl acetate in methylethylketone and in ethyl alcohol solution using the gamma radiation as initiator was projected and built. The molecular weights of the polymers obtained by irradiation with gamma rays in methylethylketone and in ethyl alcohol solution were 33,000 and 44,000g\\/mol, respectively. From the characterization

A. C Mesquita; M. N Mori; J. M Vieira; L. G. Andrade e Silva

2002-01-01

57

Functional polyolefins: poly(ethylene)-graft-poly(tert-butyl acrylate) via atom transfer radical polymerization from a polybrominated alkane.  

PubMed

Poly(cis-cyclooctene) is synthesized via ring-opening metathesis polymerization in the presence of a chain-transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert-butyl acrylate (tBA) via Cu-catalyzed atom transfer radical polymerization (ATRP) from the non-activated secondary alkyl bromide moieties finally results in PE-g-PtBA copolymer brushes. By varying the reaction conditions, a series of well-defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T(m) with increasing grafting density. PMID:22095785

Xu, Guangjuan; Wang, Dongren; Buchmeiser, Michael R

2012-01-16

58

Renewable and functional wood materials by grafting polymerization within cell walls.  

PubMed

A "grafting-from" polymerization approach within and at the complex and heterogeneous macromolecular assembly of wood cell walls is shown. The approach allows for the implementation of novel functionalities in renewable and functional wood-based materials. The native wood structure is retained and used as a hierarchical multiscale framework for a modular two-step polymerization process. The versatility and potential of the approach is shown by a polymerization of either hydrophobic or hydrophilic and pH-responsive monomers in the wood structure. Characterization of the modified wood reveals the presence of polymer in the cell wall, and the new properties of these wood materials are discussed. PMID:24616291

Cabane, Etienne; Keplinger, Tobias; Merk, Vivian; Hass, Philipp; Burgert, Ingo

2014-04-01

59

The Synthesis of Cellulose Graft Copolymers Using Cu(0)-Mediated Polymerization  

NASA Astrophysics Data System (ADS)

Cellulose is the most abundant renewable polymer on the planet and there is great interest in expanding its use beyond its traditional applications. However, its hydrophilicity and insolubility in most common solvent systems are obstacles to its widespread use in advanced materials. One way to counteract this is to attach hydrophobic polymer chains to cellulose: this allows the properties of the copolymer to be tailored by the molecular weight, density, and physical properties of the grafts. Two methods were used here to synthesize the graft copolymers: a 'grafting-from' approach, where synthetic chains were grown outward from bromoester moieties on cellulose (Cell-BiB) via Cu(0)-mediated polymerization; and a 'grafting-to' approach, where fully formed synthetic chains with terminal sulfide functionality were added to cellulose acetate with methacrylate functionality (CA-MAA) via thiol-ene Michael addition. The Cell-BiB was synthesized in the ionic liquid 1-butyl-3-methylimidazolium chloride and had a degree of substitution of 1.13. Polymerization from Cell-BiB proceeded at similar but slightly slower rate than an analogous non-polymeric initiator (EBiB). The average graft density of poly(methyl acrylate) chains was 0.71 chains/ring, with a maximum of 1.0 obtained. The graft density when grafting poly(methyl methacrylate) was only 0.15, and this appeared to be due to the slow initiation of BiB groups. Using EBiB to model the reaction and improve the design should allow this to be overcome. Chain extension experiments demonstrated the living behaviour of the polymer. The CA-MAA was synthesized by esterification with methacrylic acid. Reactions of CA-MAA with thiophenol and dodecanethiol resulted in quantitative addition of the thiol to the alkene. The grafts were synthesized by Cu(0)-mediated polymerization from a bifunctional initiator containing a disulfide bond, followed by reduction to sulfides. The synthetic polymers were successfully grafted to CA-MAA but the grafting yield was limited by the low sulfide functionality. Better retention of sulfide functionality is necessary for more efficient grafting.

Donaldson, Jason L.

60

Modification of polymeric substrates using surface-grafted nanoscaffolds  

NASA Astrophysics Data System (ADS)

Surface grafting and modification of poly(acrylic acid) (PAA) were performed on nylon 6,6 carpet fibers to achieve permanent stain and soil resistance. PAA was grafted to nylon and modified with 1H, 1H-pentadecafluorooctyl amine (PDFOA) using an amidation agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). The first goal was to optimize acrylamide modification of PAA in solution. Aqueous reactions with taurine, hydroxyethyl amine, and butyl amine progressed ˜100%, while PDFOA reactions in MeOH progressed ˜80%. Reaction products precipitated at 77% butyl or 52% PDFOA acrylamide contents. The second goal was to optimize the PAA grafting process. First, PAA was adsorbed onto nylon 6,6 films. Next, DMTMM initiated grafting of adsorbed PAA. PAA surface coverage was ˜78%, determined by contact angle analysis of the top 0.1--1 nm and x-ray photoelectron spectroscopy (XPS) analysis of the top 3--10 nm. The third goal was to modify PAA grafted nylon films with butyl amine and PDFOA. Randomly methylated beta-cyclodextrin (RAMEB) solubilized PDFOA in water. Contact angle detected ˜100% surface reaction for each amine, while XPS detected ˜77% butyl amine (H2O) and ˜50% for PDFOA (MeOH or H2O pH = 7) reactions. In H2O pH = 12, the PDFOA reaction progressed ˜89%, perhaps due to greater efficiency, access and solubility. The fourth goal was to perform surface depth profiling via angle-resolved XPS analysis (ARXPS). The PAA surface coverage from contact angle and XPS was confirmed. Further, adsorbed PAA was thicker than grafted PAA, supporting the theory that PAA adsorption occurs in thick layers onto nylon followed by DMTMM-activated spreading and grafting of thinner PAA layers across the surface. The PDFOA reaction in McOH produced a highly fluorinated but thin exterior and an unreacted PAA interior. The PDFOA reaction in H 2O pH = 12 produced a completely fluorinated exterior and highly fluorinated interior. Thus surface modification levels from contact angle and XPS were confirmed. The final goal was to PAA-graft and PDFOA-modify nylon 6,6 fabrics and carpets. PDFOA modification achieved significant water and oil repellency. Stainblocking was slightly improved for ionized PAA-g-nylon and greatly improved for PDFOA-modified PAA-g-nylon. However, traditional stainblockers may be necessary to completely prevent dye penetration into carpet tufts.

Thompson, Kimberlee Fay

61

Surface modification of cellulose nanowhisker throughout graft polymerization of 2-ethyl-2-oxazoline.  

PubMed

The cellulose nanocrystals, prepared by acid hydrolysis of cotton linter, consisted of slender rods with an average length of 173 nm and diameter of 80 nm, respectively. The surface of obtained cellulose nanocrystals was chemically modified using tosyl chloride and then tosylated cellulose nanowhisker was used as macroinitiator for cationic ring opening graft polymerization of 2-ethyl-2-oxazoline monomer. The occurrence of chemical modification was evaluated by FTIR and (1)H NMR spectroscopies. Finally cellulose-g-POX was hydrolysed in acidic condition and therefore cellulose nanowhisker-g-PEI was prepared. X-ray diffraction measurements showed that the initial crystalline structure of CNW (Type I?) was changed during graft polymerization and grafted POX in the surface of CNW was in amorphous form and DLS measurements showed that the hydrodynamic dimension of the resulted product is about 135 nm. PMID:23769522

Dadkhah Tehrani, Abbas; Neysi, Elham

2013-08-14

62

Interfacial Polymerization of Polyaniline Nanofibers Grafted to Au Surfaces.  

National Technical Information Service (NTIS)

In this work, polyaniline/poly(sulfonated styrene) nanofiber composites were prepared by an interfacial method. The in-situ polymerization technique of these PANI nanofibers in the presence of sulfonated polystyrene allowed for the growth of PANI 2-D nano...

D. D. Sawall R. M. Villahermosa R. A. Lipeles A. R. Hopkins

2004-01-01

63

The effects of early postoperative radiation on vascularized bone grafts  

SciTech Connect

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Evans, H.B.; Brown, S.; Hurst, L.N. (Division of Plastic and Reconstructive Surgery, University of Western Ontario, London (Canada))

1991-06-01

64

A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner  

NASA Astrophysics Data System (ADS)

Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly ? radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of ? radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of ? radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

Barsbay, Murat; Güven, Olgun

2009-12-01

65

Radiation grafting of styrene on starch with high efficiency  

NASA Astrophysics Data System (ADS)

Wheat starch grafted with polystyrene (PS-g-starch) was synthesized via polymerization grafting of styrene on starch by gamma-ray. The effects of starch/styrene weight ratio, and amount of applied doses (5-40 kGy) on the percentage of grafting, G (%), were investigated. The results showed that G (%) increased with increasing starch content. The optimum condition, starch/styrene weight ratio 1/3 and the applied dose 10 kGy, led to 252.9% of grafting. The obtained graft copolymer was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and scanning electron microscopy. FTIR spectroscopy as well as the XRD analysis exhibited the changes in chemical and crystalline structure of starch after grafting reaction. TGA demonstrated the changes in thermal stability of PS-g-starch copolymer. SEM micrographs indicated porous patches of PS adhering on the starch.

Sheikh, N.; Akhavan, A.; Ataeivarjovi, E.

2013-04-01

66

DFT study of the ring opening polymerization of ?-caprolactone by grafted lanthanide complexes: 1--Effect of the grafting mode on the reactivity of borohydride complexes.  

PubMed

The influence of the grafting mode of a borohydride lanthanum complex on a silica surface on the energetic (kinetic and thermodynamic parameters) of the Ring Opening Polymerization (ROP) reaction of ?-caprolactone has been studied in the framework of density functional theory (DFT). For all considered grafted catalysts (monografted, bigrafted, or bigrafted after breaking of a Si-O-Si bridge), it is shown that lanthanum borohydride grafted complexes are efficient in lactone polymerization. Moreover, the reaction pathways (leading to a -CH(2) OBH(2) chain end) are predicted to be energetically similar for the three grafting modes, indicating that all grafted modes can account for the activity for silica treated at 700 °C. The catalytic activity of the grafted complexes is also very similar to that of the homogeneous complexes. PMID:21935526

Del Rosal, Iker; Poteau, Romuald; Maron, Laurent

2011-11-14

67

Grafting polyacrylates on natural rubber latex by miniemulsion polymerization  

Microsoft Academic Search

Grafting reactions between different acrylates (methyl, ethyl, butyl, hexyl, and lauryl) and natural rubber latex (NRL) were\\u000a performed in miniemulsion. It is observed that polyacrylates with longer alkyl chain length, i.e., ?4 carbons, only produce\\u000a stable dispersions with the hydrophobic azo initiator 2,2?-azobis(2-methylbutyronitrile) (V59). Increasing the reaction temperature\\u000a from 5 to 72 °C with different initiating systems increases the gel content

Lakshiminarayanan Ragupathy; Ulrich Ziener; Graf Robert; Katharina Landfester

2011-01-01

68

Grafting of molecularly imprinted polymer to porous polyethylene filtration membranes by plasma polymerization.  

PubMed

An application of plasma-induced grafting of polyethylene membranes with a thin layer of molecularly imprinted polymer (MIP) was presented. High-density polyethylene (HDPE) membranes, "Vyon," were used as a substrate for plasma grafting modification. The herbicide atrazine, one of the most popular targets of the molecular imprinting, was chosen as a template. The parameters of the plasma treatment were optimized in order to achieve a good balance between polymerization and ablation processes. Modified HDPE membranes were characterized, and the presence of the grafted polymeric layer was confirmed based on the observed weight gain, pore size measurements, and infrared spectrometry. Since there was no significant change in the porosity of the modified membranes, it was assumed that only a thin layer of the polymer was introduced on the surface. The experiments on the re-binding of the template atrazine to the membranes modified with MIP and blank polymers were performed. HDPE membranes which were grafted with polymer using continuous plasma polymerization demonstrated the best result which was expressed in an imprinted factor equal to 3, suggesting that molecular imprinting was successfully achieved. PMID:23748644

Cowieson, D; Piletska, E; Moczko, E; Piletsky, S

2013-08-01

69

Integration of lignin and acrylic monomers towards grafted copolymers by free radical polymerization.  

PubMed

Three kinds of acrylic monomers (2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA), methyl methacrylate (MMA) and butyl acrylate (BA)) were utilized to modify the lignin (BBL) by "grafting from" free radical polymerization (FRP), respectively. Calcium chloride/hydrogen peroxide (CaCl2/H2O2) was used as initiator. Effects of monomer type and concentration, initiator concentration and polymerization time on grafting from BBL were studied. Grafting of poly (acrylic monomers) onto BBL was verified by the following characterizations and this synthesis method was found to be high efficient and selective for grafting polymerization of BBL. The presence of the BBL moiety in the backbone also resulted in higher glass transition temperature compared with the homopolymer of each monomer, and some modified copolymers also improved its thermal stability. All modifications made BBL more hydrophobic and the static contact angles of these modified copolymers were above 80°. XPS analysis revealed that the surface of these modified BBL copolymers were dominated by acrylate monomer moiety. Additionally, the BBL-g-PBA copolymers can be used as dispersion modifiers in PLA-based materials to enhance UV absorption. PMID:24742785

Liu, Xiaohuan; Xu, Yuzhi; Yu, Juan; Li, Shouhai; Wang, Jifu; Wang, Chunpeng; Chu, Fuxiang

2014-06-01

70

Synthesis of syndiotactic-polystyrene- graft-poly(methyl methacrylate) and syndiotactic-polystyrene- graft-atactic-polystyrene by atom transfer radical polymerization  

Microsoft Academic Search

Syndiotactic polystyrene graft copolymers, including syndiotactic-polystyrene-graft-poly(methyl methacrylate) and syndiotactic-polystyrene-graft-atactic-polystyrene, were synthesized by atom transfer radical polymerization (ATRP) using bromoacetylated syndiotactic polystyrene as macroinitiator and copper bromide combined with 2,2?-bipyridine as catalyst. The macroinitiator was prepared from the acid-catalyzed halogenation reaction of partially acetylated syndiotactic polystyrene, which was synthesized in a heterogeneous process with acetyl chloride and anhydrous aluminum chloride in

Yong Gao; Songqing Li; Huaming Li; Xiayu Wang

2005-01-01

71

Pre-irradiation induced emulsion co-graft polymerization of acrylonitrile and acrylic acid onto a polyethylene nonwoven fabric  

NASA Astrophysics Data System (ADS)

A pre-irradiation induced emulsion co-graft polymerization method was used to introduce acrylonitrile and acrylic acid onto a PE nonwoven fabric. The use of acrylic acid is meant to improve the hydrophilicity of the modified fabric. The kinetics of co-graft polymerization were studied. The existence of polyacrylonitrile (PAN) and poly(acrylic acid) (PAAc) graft chains was proven by Fourier transform infrared spectroscopy (FTIR) analysis. The existence of the nitrile groups in the graft chains indicates that they are ready for further amidoximation and adsorption of heavy metal ions.

Liu, Hanzhou; Yu, Ming; Ma, Hongjuan; Wang, Ziqiang; Li, Linfan; Li, Jingye

2014-01-01

72

Grafting onto polyformaldehyde fibers. [Gamma radiation  

Microsoft Academic Search

Acrylic acid (AA), acrylonitrile (AN), and acrylamide (AM) were grafted onto polyformaldehyde (PF) fibers employing ..gamma..-ray irradiation as well as benzoyl peroxide initiation. The nature of the graft copolymer obtained from a given monomer was dependent on the type of method used for the grafting reactions. This was reflected in the various characteristics of the grafted PF fibers such as

H. T. Lokhande; A. S. Salvi

1978-01-01

73

Radiation-Induced Polymerization of a Series of Vinyl Ethers  

Microsoft Academic Search

The radiation-induced polymerization of methyl, ethyl, isobutyl, isopropyl, and tert-butyl vinyl ethers was studied under super-dry conditions. Methyl vinyl ether did not polymerize at measurable rates; ethyl vinyl ether polymerized readily but with a dose rate dependence of the rate of only 0.3. The other ethers polymerized with a square-root dependence of the rate on the dose rate. Good agreement

A. M. Goineau; J. Kohler; V. Stannett

1977-01-01

74

Graft copolymers obtained by radiation grafting of methacrylic acid onto polypropylene films  

NASA Astrophysics Data System (ADS)

Direct radiation grafting of methacrylic acid (MAA) onto polypropylene films (PP) was studied. The effect of different solvents such as benzene, distilled water, dimethyl formamide, isopropanol, isopropanol/water-mixture, on the swelling and the grafting process of MAA onto (PP) films was investigated. It was found that the grafting process was enhanced under vacuum irradiation in benzene as a diluent for MAA as compared with other solvents examined. The dependence of the grafting rate on such monomer concentrations was found to be 1.2 order. The relationship between the grafting rate and film thickness gave a negative first order dependence. This grafting system proceeded by a diffusion controlled process. Some selected properties of the grafted films such as mechanical and electrical properties, swelling behaviour, and gel determination, were also investigated.

Taher, Nafossa H.; Hegazy, El-Sayed A.; Dessouki, Ahmed M.; El-Arnaouty, Magda B.

75

A new method of controlled grafting modification of chitosan via nitroxide-mediated polymerization using chitosan-TEMPO macroinitiator.  

PubMed

The controlled graft modification of chitosan has first been achieved by nitroxide-mediated polymerization using chitosan-TEMPO macroinitiator. Chitosan-TEMPO macroinitiator was obtained from the (60)Co gamma-ray irradiation of N-phthaloylchitosan and 4-hydroxy-TEMPO in DMF under argon atmosphere. The graft copolymers were characterized by (1)H nuclear magnetic resonance ((1)H NMR), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffractometer (XRD) and high performance particle sizer (HPPS). The results indicate that the graft copolymers were successfully synthesized and that the graft polymerization was well controlled by the nitroxide-mediated process. The size distribution of chitosan-g-polystyrene in benzene is very narrow, which may be associated with the "well-defined" polystyrene (PSt) onto chitosan from nitroxide-mediated polymerization. This work provides a new method to prepare chitosan grafting copolymers with controlled molecular weights and "well-defined" structures. PMID:18279949

Hua, Daoben; Deng, Weicai; Tang, Jing; Cheng, Jianxin; Zhu, Xiulin

2008-07-01

76

Surface Modification of Materials by Plasma Process and UV-induced Grafted Polymerization for Biomedical Applications  

NASA Astrophysics Data System (ADS)

Surface modification using plasma treated and graft polymerization is versatile process, with systems on the market capable of treating everything from polymer, metal, and ceramic substrates. The major advantage is that the modification is caused no substrate damage or bulk property changes. This is a very effective method to modify the surfaces of biomaterials to achieve desired physical or mechanical properties, or to induce a specific response when the device is placed in the body. They offer attractive possibilities for developing new biomaterials and for improving the performance of existing materials and devices. Hence, in this review, we describe the application of plasma treatment and graft polymerization on biomaterials field. The various applications are discussed in the following: (1) easy stripped-off wound dressing, (2) porous three-dimensional temporary scaffolds, (3) quartz crystal microbalance (QCM) base biosensors, and (4) covalent immobilization of glucose oxidase onto inorganic substrates

Chen, Ko-Shao; Chen, Su-Chen; Lien, Wei-Cheng; Tsai, Jui-Che; Ku, Yuan-An; Lin, Hong-Ru; Lin, Feng-Huei; Wu, Te-Hsing; Chen, Chia-Chieh; Chen, Tim-Mo; Chiou, Shih-Hwa

77

Plasma polymerized thin coating as a protective layer of carbon nanotubes grafted on carbon fibers  

NASA Astrophysics Data System (ADS)

Nanoparticles addition is widely studied to improve properties of carbon fiber reinforced composites. Here, hybrid carbon fiber results from grafting of carbon nanotubes (CNT) by Chemical Vapor Deposition (CVD) on the carbon fiber for mechanical reinforcement and conductive properties. Both tows and woven fabrics made of the hybrid fibers are added to the matrix for composite processing. However handling hybrid fibers may induce unwilling health risk due to eventual CNT release and a protective layer is required. A thin coating layer is deposited homogeneously by low pressure plasma polymerization of an organic monomer without modifying the morphology and the organization of grafted CNTs. The polymeric layer effect on the electrical behavior of hybrid fiber is assessed by conductivity measurements. Its influence on the mechanical properties is also studied regarding the interface adhesion between fiber and matrix. The protective role of layer is demonstrated by means of friction constraints applied to the hybrid fiber.

Einig, A.; Rumeau, P.; Desrousseaux, S.; Magga, Y.; Bai, J. B.

2013-04-01

78

Facile graft polystyrene onto multi-walled carbon nanotubes via in situ thermo-induced radical polymerization  

Microsoft Academic Search

A facile procedure was developed for the grafting of polystyrene onto the surfaces of multi-walled carbon nanotubes (MWNTs)\\u000a via the in situ thermo-induced bulk radical polymerization of styrene at the different polymerizing temperatures, in the presence\\u000a of MWNTs without any initiator added. The grafting products were validated by the dispersibility, TEM, TGA, FT-IR, and Raman\\u000a analysis. The TGA results also showed

Peng Liu

2009-01-01

79

Photo-induced graft polymerization surface modifications for the preparation of hydrophilic and low-proten-adsorbing ultrafiltration membranes  

Microsoft Academic Search

Heterogeneous surface modifications of PAN UF membranes with either simultaneous or sequential UV irradiation-initiated graft polymerizations of monomers from water solutions were studied. Previous coating with a photo-initiator (benzophenone, BP) and saturation of the monomer solutions with BP mainly promoted simultaneous graft polymerization onto the membrane surface. Photo-induced formation and thermal decomposition of peroxides were assayed with the DPPH assay

Mathias Ulbricht; Heike Matuschewski; Annett Oechel; Hans-Georg Hicke

1996-01-01

80

Grafting from ramie fiber with poly(MMA) or poly(MA) via reversible addition-fragmentation chain transfer polymerization  

Microsoft Academic Search

Reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to control the grafting of methyl methacrylate\\u000a (MMA) and methyl acrylate (MA) from natural ramie fibers substrate. The hydroxyl groups of ramie fibers were first converted\\u000a to 2-dithiobenzoyl isobutyrate as a RAFT chain transfer agent (CTA), which was further grafted with MMA or MA mediated by\\u000a the RAFT polymerization in a presence

Jing Chen; Jie Yi; Ping Sun; Zhao-Tie Liu; Zhong-Wen Liu

2009-01-01

81

Effect of diffusion on rates and molecular weights in graft polymerization  

Microsoft Academic Search

A theoretical analysis has been made of the graft polymerization process ; in terms of the quantitative interrelationship between the initiation rate R\\/sub ; i\\/, the k\\/sub p\\/\\/k\\/sub t¹² ratio of the monomer, the equilibrium ; solubility M of the monomer in the polymer, the polymer film thickness L, and the ; diffusivity D of the monomer in the polymer.

George Odian; Richard Henry; Raymond Koenig; D. Mangaraj; Le Doan Trung; Bou Chao; Arif Derman

1975-01-01

82

Graft polymerization of styrene onto starch by simultaneous cobalt-60 irradiation  

Microsoft Academic Search

Starch-g-polystyrene copolymers have been prepared by the simultaneous ⁶°Co irradiation of starch--styrene mixtures, and copolymers have been characterized with respect to weight per cent polystyrene (% add-on) and also the molecular weight and molecular weight distribution of polystyrene grafts. In a typical polymerization, 4g each of starch and styrene were blended with 1 ml water and 1.5 ml of an

George F. Fanta; Robert C. Burr; W. M. Doane; C. R. Russell

1977-01-01

83

Preparation of PhotoSensitive Degradable Polymeric Nanocapsules from Dendrimer Grafted Nano-Silica Templates  

Microsoft Academic Search

The poly-hydroxylated photo-sensitive degradable polymeric nanocapsules were prepared by the condensation of the A2-type monomer 4, 4?-Azobenzene dibenzoyl chloride (ADC) and the B3-type monomer triethanolamine (TEA) from the sacrificial nano-silica templates by a divergent approach. After the dendrimer molecules grafted on the silica nanoparticles were cross-linked with ADC, which is both the monomer and the cross-linker in this approach developed

Ruoping Shen; Bin Mu; Pengcheng Du; Peng Liu

2011-01-01

84

Gamma radiation-induced grafting of glycidyl methacrylate (GMA) onto water hyacinth fibers  

NASA Astrophysics Data System (ADS)

Water hyacinth fibers (Eichhornia crassipes) were functionalized using radiation-induced graft polymerization of glycidyl methacrylate by ?-rays from 60Co source. The simultaneous grafting technique was employed wherein the water hyacinth fibers were irradiated in nitrogen atmosphere in the presence of glycidyl methacrylate dissolved in water/methanol solvent. The effects of different grafting parameters to the grafting yield were evaluated. The optimal values of solvent, absorbed dose, dose rate, and concentration of monomer were found to be 1:3 (volume/volume) water-methanol solvent, 10 kGy, 8 kGy h-1 dose rate and 5% volume/volume glycidyl methacrylate, respectively. Using the optimum conditions, degree of grafting of approximately 58% was achieved. The grafted water hyacinth fibers were characterized using Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The results of these tests confirmed the successful grafting of glycidyl methacrylate onto water hyacinth fibers.

Madrid, Jordan F.; Nuesca, Guillermo M.; Abad, Lucille V.

2013-04-01

85

Preparation of poly(methyl methacrylate) grafted titanate nanotubes by in situ atom transfer radical polymerization  

NASA Astrophysics Data System (ADS)

This paper reports the successful preparation of core-shell hybrid nanocomposites by a 'grafting from' approach based on in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from titanate nanotubes (TNTs). Transmission electron microscope (TEM) images of the products provide direct evidence for the formation of a core-shell structure, possessing a hard core of TNTs and a soft shell of poly-MMA (PMMA). Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to determine the chemical structure, morphology, and the grafted PMMA quantities of the resulting products. The grafted PMMA content was well controlled and increased with increasing monomer/initiator ratio. Further copolymerization of hydroxyethyl methacrylate (HEMA) with PMMA-coated TNTs as initiators was realized, illustrating the 'living' characteristics of the ATRP method used in this paper.

Gao, Yuan; Gao, Xueping; Zhou, Yongfeng; Yan, Deyue

2008-12-01

86

Temperature Responsive Cellulose-graft-Copolymers via Cellulose Functionalization in an Ionic Liquid and RAFT Polymerization.  

PubMed

Well-defined cellulose-graft-polyacrylamide copolymers were synthesized in a grafting-from approach by reversible addition-fragmentation chain transfer polymerization (RAFT). A chlorine moiety (degree of substitution DS(Cl) ? 1.0) was introduced into the cellulose using 1-butyl-3-methylimidazolium chloride (BMIMCl) as solvent before being substituted by a trithiocarbonate moiety resulting in cellulose macro-chain transfer agents (cellulose-CTA) with DS(RAFT) of 0.26 and 0.41. Poly(N,N-diethylacrylamide) (PDEAAm) and poly(N-isopropylacrylamide) (PNIPAM) were subsequently grafted from these cellulose-CTAs and the polymerization kinetics, the molecular weight characteristics and the product composition were studied by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and size exclusion chromatography of the polyacrylamides after cleavage from the cellulose chains. The number-average molecular weights, Mn, of the cleaved polymers ranged from 1100 to 1600 g mol(-1) for PDEAAm (dispersity ? = 1.4-1.8) and from 1200 to 2600 g mol (-1) for PNIPAM (? = 1.7-2.1). The LCST behavior of the cellulose-graft-copolymers was studied via the determination of cloud point temperatures, evidencing that the thermoresponsive properties of the hybrid materials could be finely tuned between 18 and 26 °C for PDEAAm and between 22 and 26 °C for PNIPAM side chains. PMID:24833429

Hufendiek, Andrea; Trouillet, Vanessa; Meier, Michael A R; Barner-Kowollik, Christopher

2014-07-14

87

Graft polymerization onto nano-sized SiO 2 surface and its application to the modification of PBT  

Microsoft Academic Search

Nano-silica was used to modify thermoplastics polybutylene terephthalate (PBT) in order to improve the properties. Before being filled into PBT, nano-silica was subjected to graft modification. The graft polymerization of PBT prepolymer was performed onto the surface of the nano-particles and the grafted nano-silica was characterized with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, sedimentation experiment, transmission

Jianfei Che; Baoyong Luan; Xujie Yang; Lude Lu; Xin Wang

2005-01-01

88

Polyglycerol dendrimers immobilized on radiation grafted poly-HEMA hydrogels: Surface chemistry characterization and cell adhesion  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of poly(2-hydroxyethylmethacrylate) (PHEMA) on low density polyethylene (LDPE) films and subsequent immobilization of poly(glycerol) dendrimer (PGLD) has been performed with the aim to improve cell adhesion and proliferation on the surface of the polymer, in order to enhance their properties for bone tissue engineering scaffolding applications. Radiation grafting of PHEMA onto LDPE was promoted by ?-ray radiation. The covalent immobilization of PGLD on LDPE-g-PHEMA surface was performed by using a dicyclohexyl carbodiimide (DCC)/N,N-dimethylaminopyridine (DMAP) method. The occurrence of grafting polymerization of PHEMA and further immobilization of PGLD was quantitatively confirmed by photoelectron spectroscopy (XPS) and fluorescence, respectively. The LDPE-g-PHEMA surface topography after PGLD coupling was studied by atomic force microscopy (AFM). The hydrophilicity of the LDPE-g-PHEMA film was remarkably improved compared to that of the ungrafted LDPE. The core level XPS ESCA spectrum of PHEMA-grafted LDPE showed two strong peaks at 286.6 eV (from hydroxyl groups and ester groups) and 289.1 eV (from ester groups) due to PHEMA brushes grafted onto LDPE surfaces. The results from the cell adhesion studies show that MCT3-E1 cells tended to spread more slowly on the LDPE-g-PHEMA than on the LDPE-g-PHEMA-i-PGLD.

Higa, Olga Z.; Faria, Henrique Antonio Mendonça; de Queiroz, Alvaro A. A.

2014-05-01

89

Radiation-induced grafting of acrylic acid onto polyethylene filaments  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of acrylic acid onto high density polyethylene (PE) filaments was carried out in order to raise softening temperature and impart flame retardance and hydrophilic properties. Mutual ?-irradiation method was employed for the grafting in a mixture of acrylic acid (AA), ethylene dichloride and water containing a small amount of ferrous ammonium sulfate. The rate of grafting was very low at room temperature. On the other hand, large percent grafts were obtained when the grafting was performed at an elevated temperature. Activation energy for the initial rate of grafting was found to be 17 {kcal}/{mol} between 20 and 60°C and 10 {kcal}/{mol} between 60 and 80°C. Original PE filament begins to shrink at 70°C, show maximum shrinkage of 50% at 130°C and then breaks off at 136°C. When a 34% AA graft is converted to metallic salt such as sodium and calcium, the graft filament retains its filament form even above 300°C and gives maximum shrinkage of 15%. Burning tests by a wire-netting basket method indicate that graft filaments and its metallic salts do not form melting drops upon burning and are self-extinguishing. Original PE filament shows no moisture absorption, however, that of AA-grafted PE increases with increasing graft percent. The sodium salt of 15% graft shows the same level of moisture regain as cotton. The AA-grafted PE filament and its metallic salts can be dyed with cationic dyes even at 1% graft. Tensile properties of PE filament is impaired neither by grafting nor by conversion to metallic salts.

Kaji, K.; Okada, T.; Sakurada, I.

90

[Flocculation of kaolin suspensions by chitosan grafted ternary polymerization flocculant].  

PubMed

Flocculation of kaolin suspensions using ternary polymerization flocculant (CAS) synthesized by chitosan (CTS), acrylamide and ethyl acrylate quaternary ammonium salt was investigated in lab-scale. It was found that CAS had more advantages such as higher flocculation efficiency, lesser dosage and wider pH flocculation range than CTS. CAS was insignificantly exposed to the properties of suspended particles, so preferable flocculation efficiency by it could be obtained both with distilled water and tap water kaolin suspensions. The optimal dosage for CAS was only one-tenth of that of CTS in neutral condition. Good flocculation performance was observed in the pH range of 2.0-11.0 at the dosage of 0.5 mg x L(-1) CAS, and the turbidity removal rates were about 95%. It was also shown that flocculation efficiency was very sensitive to the raw turbidity of kaolin suspensions. At less than 0.5 mg x L(-1) of CAS dose, the higher raw turbidity of the suspension contrarily yielded a lower removing rate. However, when the dosage of CAS was more than 0.5 mg x L(-1), the flocculation efficiency increased with increasing the raw turbidity of kaolin. When the dosage was more than 1.0 mg x L(-1), turbidity removal efficiencies exceeding 85% could be achieved in overall experimental turbidities from 10 to 160 NTU. iPDA-100 device was used to follow the particle aggregation process. And also zeta potential values of particles,floc sizes, shape analyses were presented. It is presumed that the flocculation induced by CAS is dominated by charge patch mechanism and bond bridging. The flocculation reactivity of kaolin suspensions exhibits a dynamic changing, which is simultaneously responsible for several kinds of driving forces. PMID:18637345

Hu, Yong-you; Li, Si-qing; Guo, Yan-ping; Cheng, Jian-hua

2008-04-01

91

Surface modification of active metals through atom transfer radical polymerization grafting of acrylics  

NASA Astrophysics Data System (ADS)

The objective of this work is to investigate the fundamentals of surface-initiated atom transfer radical polymerization (s-ATRP) on metal substrates. Acrylic polymers were grafted from active metal surfaces such as cold rolled steel (CRS), stainless steel (SS) and nickel (Ni) through s-ATRP. Severe deactivation was found with copper bromide bipyridine catalyst. Controlled polymerization with relatively low polydispersities, 1.18-1.35, was achieved using iron bromide triphenylphosphine catalyst. Polymer films up to 80 nm in thickness were obtained within 80 min. Grafting densities were estimated to be 0.58 chains/nm 2 for CRS-g-PMMA, 0.55 chains/nm 2 for Ni-g-PMMA, 0.18 chains/nm 2 for SS-g-PMMA, and 0.66 chains/nm 2 for SS-g-PDMAEMA. Electrochemical experiments were also carried out to measure the polarization resistance and corrosion potential of CRS-g-PMMA substrates. Metal surfaces with grafted brush polymer coatings showed significant corrosion resistance. This work demonstrated that the surface-initiated ATRP is a versatile means for the surface modification of active metals with well-defined and functionalized polymer brushes.

Gong, Rachel; Maclaughlin, Shane; Zhu, Shiping

2008-08-01

92

Modeling of thermal and radiative aging of polymeric cable materials  

Microsoft Academic Search

It is of critical importance to safety in the nuclear power industry to estimate the lifetime of polymeric materials in an environment featuring elevated temperatures and radiation. To this end, the authors are examining the aging of polymeric materials, in cables and other components in nuclear reactor containments by comparing aging processes for a variety of materials under natural conditions

Montgomery T. Shaw; Yong-Ming Liu

1996-01-01

93

Syntheses of amine-type adsorbents with emulsion graft polymerization of glycidyl methacrylate  

NASA Astrophysics Data System (ADS)

Glycidyl methacrylate (GMA) which was precursor monomer for the synthesis of metal ion adsorbent was emulsified by surfactant of Tween 20 (Tw-20). The emulsion of 5% GMA in the water was stable for 48 h at Tw-20 concentration of 0.5%. Graft polymerization of GMA on polyethylene fiber was carried out in the emulsion state at various pre-irradiation doses. Degree of grafting (Dg) reached 103%, 301% and 348% for 1 h grafting at 40 °C with pre-irradiation of 10, 30 and 40 kGy, respectively. But the Dg was depressed when the pre-irradiation dose was over 50 kGy since cross-linking occurred simultaneously in the trunk polymer. Dg decreased with increment of Tw-20 concentration in emulsion of 5% GMA at pre-irradiation of 40 kGy. The three kinds of amine-type adsorbents were synthesized by reacting diethylenetriamine (DETA), triethylenetetramine (TETA) and ethylenediamine (EDA) with GMA-grafted polyethylene fiber. The synthesized EDA-type adsorbent had the highest selectivity against U ion and the distribution coefficient was 2.0 × 10 6.

Seko, N.; Bang, L. T.; Tamada, M.

2007-12-01

94

Temperature-sensitive hydrogels by graft polymerization of chitosan and N-isopropylacrylamide for drug release.  

PubMed

Thermo-responsive polysaccharidic hydrogels were designed and synthesized by a free radical induced grafting procedure. Chitosan was chosen as biopolymer to impart biocompatibility and biodegradability to the macromolecular systems, while N-isopropylacrylamide (NIPAAm) was selected as co-monomer responsive for the thermo-sensitive properties. Ammonium persulfate was the initiator system and different polymeric networks have been synthesized by modulating the amount of NIPAAm in the polymerization feed. The resulting hydrogels were proposed as drug delivery devices and their performance was evaluated by using Diclofenac sodium salt as a model drug. Hydrogels were carefully characterized by FT-IR spectrophotometry, calorimetric analyses and swelling behavior in a temperature range of 15-45°C. Finally, to verify the suitability of these hydrogels as thermo-responsive devices, the drug release profiles were studied performing in vitro experiments around the swelling-shrinking transition temperatures of the macromolecular systems. PMID:22200242

Spizzirri, Umile Gianfranco; Iemma, Francesca; Cirillo, Giuseppe; Altimari, Ilaria; Puoci, Francesco; Picci, Nevio

2013-01-01

95

Preparation of polymer decorated graphene oxide by ?-ray induced graft polymerization  

NASA Astrophysics Data System (ADS)

Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by ?-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes.Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by ?-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes. Electronic Supplementary Information (ESI) available: XPS and photos. See DOI: 10.1039/c2nr11724j

Zhang, Bowu; Zhang, Yujie; Peng, Cheng; Yu, Ming; Li, Linfan; Deng, Bo; Hu, Pengfei; Fan, Chunhai; Li, Jingye; Huang, Qing

2012-02-01

96

DFT study of the ring opening polymerization of ?-caprolactone by grafted lanthanide complexes: 2--Effect of the initiator ligand.  

PubMed

The influence of the initiator ligand on the Ring Opening Polymerization (ROP) of ?-caprolactone by lanthanide complexes grafted on silica have been investigated by means of density functional theory (DFT) calculations. Three different initiator ligands (alkyl, dialkylamido and borohydride) and three grating modes (mono-grafted, bi-grafted or bi-grafted after breaking of a Si-O-Si bridge) have been considered. This study highlights that lanthanum grafted complexes (alkyl, amide or borohydride) are active in lactone polymerization. In any case the reaction process is demonstrated to be similar to the one found for homogeneous catalysts. However, even if the different grafting modes are energetically equivalent for the ?-caprolactone ROP initiation reaction, some differences are observed according to the ligand involved in the initiation reaction. In agreement with experimental data, grafted lanthanide amides rapidly polymerise the ?-caprolactone. The grafted alkyl lanthanum complexes are also predicted to be very efficient catalysts. The borohydride is thus predicted to be the least efficient due to the difficulties in the ring opening. Indeed, the rate-determining step is the nucleophilic attack for the methyl and dialkylamido ligands (occuring with a low barrier) whereas it is the ring opening for the borohydride ligands (highest barrier) and the formation of -CH(2)C(=O)(X) (X = CH(3) or NMe(2)) terminal group is more favorable than that of a -CH(2)OBH(2) end group. PMID:21918766

Del Rosal, Iker; Poteau, Romuald; Maron, Laurent

2011-11-14

97

High throughput atmospheric pressure plasma-induced graft polymerization for identifying protein-resistant surfaces.  

PubMed

Three critical aspects of searching for and understanding how to find highly resistant surfaces to protein adhesion are addressed here with specific application to synthetic membrane filtration. They include the (i) discovery of a series of previously unreported monomers from a large library of monomers with high protein resistance and subsequent low fouling characteristics for membrane ultrafiltration of protein-containing fluids, (ii) development of a new approach to investigate protein-resistant mechanisms from structure-property relationships, and (iii) adaptation of a new surface modification method, called atmospheric pressure plasma-induced graft polymerization (APP), together with a high throughput platform (HTP), for low cost vacuum-free synthesis of anti-fouling membranes. Several new high-performing chemistries comprising two polyethylene glycol (PEG), two amines and one zwitterionic monomers were identified from a library (44 commercial monomers) of five different classes of monomers as strong protein-resistant monomers. Combining our analysis here, using the Hansen solubility parameters (HSP) approach, and data from the literature, we conclude that strong interactions with water (hydrogen bonding) and surface flexibility are necessary for producing the highest protein resistance. Superior protein-resistant surfaces and subsequent anti-fouling performance was obtained with the HTP-APP as compared with our earlier HTP-photo graft-induced polymerization (PGP). PMID:22123600

Gu, Minghao; Kilduff, James E; Belfort, Georges

2012-02-01

98

PEG molecular net-cloth grafted on polymeric substrates and its bio-merits.  

PubMed

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling "PEG molecular net-cloth" on a solid surface, fabricated using a novel "visible light induced surface controlled graft cross-linking polymerization" (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications. PMID:24845078

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-01-01

99

PEG Molecular Net-Cloth Grafted on Polymeric Substrates and Its Bio-Merits  

PubMed Central

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling “PEG molecular net-cloth” on a solid surface, fabricated using a novel “visible light induced surface controlled graft cross-linking polymerization” (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications.

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-01-01

100

Effect of grafted polymeric foaming agent on the structure and properties of nano-silica\\/polypropylene composites  

Microsoft Academic Search

To promote dispersion of nano-silica in polypropylene (PP), a polymerizable foaming agent p-vinylphenylsulfonylhydrazide was synthesized and grafted onto the nanoparticles via free-radical polymerization. It was found that the grafted poly(p-vinylphenylsulfonylhydrazide) played dual role when being melt mixed with PP. The side sulfonylhydrazide groups were gasified to form polymer bubbles, leading to rapid inflation of the surrounding matrix that pulled apart

Li Feng Cai; Xian Bo Huang; Min Zhi Rong; Wen Hong Ruan; Ming Qiu Zhang

2006-01-01

101

Surface modification of commercial aromatic polyamide reverse osmosis membranes by graft polymerization of 3-allyl-5,5-dimethylhydantoin  

Microsoft Academic Search

A commercially available aromatic polyamide reverse osmosis (RO) membrane was chemically modified to improve its chlorine resistance and anti-biofouling property. The raw RO membranes were modified by free-radical graft polymerization of 3-allyl-5,5-dimethylhydantoin (ADMH) using 2,2?-azobis(isobutyramidine) dihydrochloride as an initiator. Attenuated total reflective Fourier transform infrared spectra (ATR-FTIR) verified the successful graft of ADMH on the raw membrane surfaces. It was

Xinyu Wei; Zhi Wang; Zhe Zhang; Jixiao Wang; Shichang Wang

2010-01-01

102

Radiation graft copolymer of acrylic acid onto EVA  

Microsoft Academic Search

The structure of the radiation graft copolymer of acrylic acid onto EVA has been studied by infrared spectroscopy and XPS. It was found that along with the main peal C1m there is a photoelectron peak at 288.5eV attributed to --OH group in XPS spectra and the content of its area in XPS increases with increasing of grafting degree of EVA.

J. T. Che; W. X. Zhang

1993-01-01

103

Study on radiation-induced grafting of styrene onto chitin and chitosan  

Microsoft Academic Search

Radiation-induced grafting of styrene onto chitin and chitosan powder was performed at room temperature. The effect of various conditions such as absorbed dose, solvent and oxygen on grafting was investigated. The grafting yield increased with the increase in absorbed dose. At the same dose, the grafting yield of styrene on chitosan was higher than that on chitin. The grafting reaction

Liu Pengfei; Zhai Maolin; W. Jilan

2001-01-01

104

Radiation-induced grafting of glycidyl methacrylate onto cotton fabric waste and its modification for anchoring hazardous wastes from their solutions.  

PubMed

Ion exchange adsorbents based on cellulosic fabric wastes carrying sulfonic acid and amine functional groups were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) with subsequent chemical modification of the epoxy groups of poly-GMA graft chains with sodium sulfite/H(2)SO(4) and triethylamine, respectively. The conversion of epoxy groups into the functional groups was investigated. Factors affecting on grafting process such as radiation dose, monomer concentration and solvent were studied. The synthesized adsorbent and its applications in the removal of different types of hazardous pollutants e.g. acidic dye, cobalt, dichromate and phenols from aqueous solution were also studied. PMID:19297095

Sokker, Hesham H; Badawy, Sayed M; Zayed, Ehab M; Nour Eldien, Faten A; Farag, Ahmad M

2009-08-30

105

Combination of “living” nitroxide-mediated and photoiniferter-induced “grafting from” free-radical polymerizations: From branched copolymers to unimolecular micelles and microgels  

Microsoft Academic Search

We report on solution properties of lightly grafted copolymers composed of polystyrene (PS) backbone (degree of polymerization of PS backbone, Nb=95) and variable length of poly(tert-butyl methacrylate) P(tBuMA) side chains (degree of polymerization of side chains, Nsc=14–222) at fixed number of grafting sites n=11 and polydispersity index (Mw\\/Mn) ranging from 1.05 to 2.63. Synthesis of these graft copolymers is based

Daniel Gromadzki; Sergey Filippov; Miloš Netopilík; Ri?ardas Makuška; Alexander Jigounov; Josef Pleštil; Ji?í Horský; Petr Št?pánek

2009-01-01

106

Additive effects common to radiation grafting and wood plastic composite formation  

NASA Astrophysics Data System (ADS)

A range of additives has been developed for enhancing grafting yields in a variety of systems initiated by ionizing radiation. Cellulose has been adopted as the predominant naturally occurring model backbone polymer in these studies because of its structural relationship to wood which is the reference substrate for the work reported in the related second part of this paper concerning composites. Some experiments have been performed with the other major naturally occurring polymer, wool. For comparison purposes with synthetic materials, some studies have also been performed with polypropylene as trunk polymer. Styrene has been used as a predominant monomer in grafting with some experiments utilizing the acrylates like methyl methacrylate. The role of solvent in grafting has been evaluated. UV has been used as initiator to replace ionizing radiation for certain experiments. The additives used were mineral acids, lithium salts, multifunctional acrylates and their methacrylate analogues, urea, oligomer acrylates, silane, fluorinated alkyl esters and thermal free radical initiators. A mechanism to explain the additive effect in terms of reagent partitioning has been proposed. The most efficient of the additives in grafting have been applied to the radiation synthesis of wood-polymer composites using two different types of wood, namely simul from Bangladesh and Pinus radiata from Australia with two different monomers with and without solvent, namely butyl methacrylate and methyl methacrylate. The effect of the additives on the physical properties, such as polymer loading and tensile strength, of the wood composites were determined. The partition concept developed for grafting has been used to explain the reactivity of the additives in wood plastic formation. The polymerization of monomers in wood plastic systems is shown to be related to simple homopolymerization of monomers in solution, a reaction which is also shown to be capable of interpretation in terms of partition phenomena.

Garnett, John L.; Ng, Loo-Teck

1996-08-01

107

Radiation induced grafting of acrylic acid onto extruded polystyrene surface  

NASA Astrophysics Data System (ADS)

Polystyrene materials with good solubility in liquid scintillation cocktails are used to wipe off different types of surfaces in order to determine the tritium removable contamination with the help of a liquid scintillation counter. This paper analyses hydrophilic surface modifications by radiation induced grafting of acrylic groups onto extruded polystyrene plates. Two grafting methods were used: (a) exposure of extruded polystyrene plates, immersed in aqueous acrylic acid solution, to a gamma radiation of a Co-60 source, and (b) exposure of extruded polystyrene plates to a Co-60 source, followed by the immersion of extruded polystyrene plates in aqueous acrylic acid solution. The grafting of acrylic was proved by IR spectrometry and by radiometric methods using acrylic acid labelled with tritium.

Fugaru, Viorel; Bubueanu, George; Tuta, Catalin

2012-09-01

108

Effects of additives on the photo-induced grafting polymerization of N-isopropylacrylamide gel onto PET film and PP nonwoven fabric surface  

Microsoft Academic Search

In this study, the thermosensitive gels were grafted onto plasma-activated polyethylene terephthalate (PET) film and polypropylene (PP) nonwoven fabric surface. The Ar* plasma pretreatment was carried out and subsequent photo-induced surface graft polymerization was employed to graft the N-isopropylacrylamide (NIPAAm). The effects of additives during the grafting were accessed. The additives used were ammonium peroxodisulfate (APS, initiator), N,N,N?,N?-tetra-methylethylene-diamine (TEMED, promoter)

Ko-Shao Chen; Jui-Che Tsai; Chih-Wei Chou; Mu-Rong Yang; Jen-Ming Yang

2002-01-01

109

Controlling the cell adhesion property of silk films by graft polymerization.  

PubMed

We report here a graft polymerization method to improve the cell adhesion property of Bombyx mori silk fibroin films. B. mori silk has evolved as a promising material for tissue engineering because of its biocompatibility and biodegradability. However, silk's hydrophobic character makes cell adhesion and proliferation difficult. Also, the lack of sufficient reactive amino acid residues makes biofunctionalization via chemical modification challenging. Our study describes a simple method that provides increased chemical handles for tuning of the surface chemistry of regenerated silk films (SFs), thus allowing manipulation of their bioactivity. By grafting pAAc and pHEMA via plasma etching, we have increased carboxylic acid and hydroxyl groups on silk, respectively. These modifications allowed us to tune the hydrophilicity of SFs and provide functional groups for bioconjugation. Our strategy also allowed us to develop silk-based surface coatings, where spatial control over cell adhesion can be achieved. This control over cell adhesion in a particular region of the SFs is difficult to obtain via existing methods of modifying the silk fibroin instead of the SF surface. Thus, our strategy will be a valuable addition to the toolkit of biofunctionalization for enhancing SFs' tissue engineering applications. PMID:24650047

Dhyani, Vartika; Singh, Neetu

2014-04-01

110

EUV lithographic radiation grafting of thermo-responsive hydrogel nanostructures  

NASA Astrophysics Data System (ADS)

Nanostructures of the thermoresponsive poly( N-isopropyl acrylamide) (PNIPAAm) and of PNIPAAm-block-poly(acrylic acid) copolymers were produced on poly(tetrafluoroethylene-co-ethyelene) (ETFE) films using extreme ultraviolet (EUV) lithographic exposure with subsequent graft-polymerization. The phase transition of PNIPAAm nanostructures at the low critical solution temperature (LCST) at 32 °C was imaged by atomic force microscopy (AFM) phase contrast measurements in pure water. Results show a higher phase contrast for samples measured below the LCST temperature than for samples above the LCST, proving that the soft PNIPAAm hydrogel transforms into a much more compact conformation above the LCST. EUV lithographic exposures were combined with the reversible addition-fragment chain transfer (RAFT)-mediated polymerization using cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agent to synthesize PNIPAAm block-copolymer nanostructures.

Farquet, Patrick; Padeste, Celestino; Solak, Harun H.; Gürsel, Selmiye Alkan; Scherer, Günther G.; Wokaun, Alexander

2007-12-01

111

GRAFTING VINYL POLYMERS ONTO CELLULOSE BY HIGH ENERGY RADIATION. I. HIGH ENERGY RADIATION-INDUCED GRAFT COPOLYMERIZATION OF STYRENE ONTO CELLULOSE  

Microsoft Academic Search

Styrene was grafted onto cellulose in the form of cotton linters, cotton ; cloth, and rayon by ionizing radiation. Styrene was brought into intimate ; contact with cellulose by extension of the inclusion technique, and graft ; copolymers were prepared by exposure to high energy electrons or to gamma rays ; from Co⁶°. Substantial grafting was obtained by irradiation in

R. Y.-M. Huang; B. Immergut; E. H. Immergut; W. H. Rapson

1963-01-01

112

Tolerance of autologous and allogeneic bone grafts to therapeutic radiation in humans  

Microsoft Academic Search

Purpose: To examine the effect of perioperative irradiation on bone graft healing and functional integrity.Methods and Materials: Fifty-five bone grafts (10 autologus and 45 allogeneic) performed between 1978 and 1995 were evaluated retrospectively. Sixteen received preoperative radiation, 11 received postoperative, and 13 were treated with a combination of pre- and postoperative radiation. Fifteen nonirradiated grafts were randomly selected to serve

Matthew A Spear; Damian E Dupuy; Jenine J Park; Elkan F Halpern; Ira J Spiro

1999-01-01

113

Space radiation resistant transparent polymeric materials  

NASA Technical Reports Server (NTRS)

A literature search in the field of ultraviolet and charged particle irradiation of polymers was utilized in an experimental program aimed at the development of radiation stable materials for space applications. The rationale utilized for material selection and the synthesis, characterization and testing performed on several selected materials is described. Among the materials tested for ultraviolet stability in vacuum were: polyethyleneoxide, polyvinylnaphthalene, and the amino resin synthesized by the condensation of o-hydroxybenzoguanamine with formaldehyde. Particularly interesting was the radiation behavior of poly(ethyleneoxide), irradiation did not cause degradation of optical properties but rather an improvement in transparency as indicated by a decrease in solar absorptance with increasing exposure time.

Giori, C.; Yamauchi, T.

1977-01-01

114

Grafting polymer nanoshell onto the exterior surface of mesoporous silica nanoparticles via surface reversible addition-fragmentation chain transfer polymerization  

Microsoft Academic Search

Reversible addition-fragmentation chain transfer (RAFT) functionalities were anchored to the exterior surface of mesoporous silica nanoparticles (MSNs) without changing the mesoporous structure, RAFT polymerization of styrene was subsequently conducted to graft polystyrene (PSt) onto the exterior surface of MSNs, forming a novel core–shell nanostructure with a mesoporous core and a polymer nanoshell. Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron

Chun-Yan Hong; Xin Li; Cai-Yuan Pan

2007-01-01

115

Surface modification of non-woven fabric by DC pulsed plasma treatment and graft polymerization with acrylic acid  

Microsoft Academic Search

Direct-current pulsed plasma treatment (DPPT) followed by thermal-induced graft polymerization with acrylic acid (AA) was used to modify poly(ethylene terephthalate)\\/polyethylene (PET\\/PE) non-woven fabric (NWF) in this study. The water contact angle of plasma modified NWF decreased sharply with DPPT time in 4s. The water content of the NWF increased with DPPT time and levelled off after 30s. Chemical analysis by

Jyh-Ping Chen; Yi-Ping Chiang

2006-01-01

116

Comparison of pre-irradiation and mutual grafting of 2-chloroacrylonitrile on cellulose by gamma-irradiation  

NASA Astrophysics Data System (ADS)

Radiation-induced graft polymerization is one of the best methods for obtaining materials with new properties. In this work, radiation grafting of 2-chloroacrylonitrile to cellulose by mutual and pre-irradiation grafting methods was investigated. The grafting yield was enhanced by applying the emulsion grafting method. The grafting yield determined in the above systems was observed as 27% at highest and 6% at lowest. The effects of concentration of monomer, reaction time and reaction temperature on grafting yield were studied. Evidence of grafting has been based on the comparative studies of cellulose and grafted cellulose by infrared spectroscopy, thermal analysis and contact angle measurement. Grafting enhances thermal stability of cellulose backbone.

?olpan, Dilek; Torun, Murat; Güven, Olgun

2010-03-01

117

Dual stimuli-responsive N-phthaloylchitosan-graft-(poly(N-isopropylacrylamide)-block-poly(acrylic acid)) copolymer prepared via RAFT polymerization.  

PubMed

In order to develop stimuli-responsive hydrogel, chitosan graft copolymer with chitosan back-bone and poly(N-isopropylacrylamide)-block-poly(acrylic acid) (PNIPAAm-b-PAA) branch chains was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization in DMF. The chain transfer agent was obtained by modification of chitosan with 3-benzylsulfanyl thiocarbonylsulfanyl propionic acid (BPATT) with 68% the degree of substitute. The graft polymerizations possessed controlled/living characteristics. The behavior of the graft copolymer in aqueous solution was investigated by dynamic light scattering, transmission electron microscopy, and UV-visible spectrophotometer. N-Phthaloylchitosan-graft-(poly(N-isopropylacrylamide)-block-poly(acrylic acid)) copolymer (N-phthaloylchitosan-g-(PNIPAAm-b-PAA)) could assemble to micelles in aqueous solution in range of 200-300 nm with narrow size distribution, and the hydrodynamic diameter could be controlled dependent on length of branch chains and temperature. The LCST values of micelle could be modulated from 34 to 40 °C by controlling the constitution of branch chains, pH, and concentration. PMID:23218351

Zhang, Ke; Wang, Zhengke; Li, Youliang; Jiang, Zhiqiang; Hu, Qiaoling; Liu, Minying; Zhao, Qingxiang

2013-01-30

118

Polypropylene membrane surface modification by RAFT grafting polymerization and TiO 2 photocatalysts immobilization for phenol decomposition in a photocatalytic membrane reactor  

Microsoft Academic Search

The main technical barriers that impede photocatalytic membrane reactor (PMR) commercialization remain on the post-recovery of the catalyst particles after water treatment. To overcome this problem, surface modification of polypropylene macroporous membrane was performed with the technique of photoinduced reversible addition-fragmentation chain transfer grafting polymerization of acrylic acid. Titanium oxide photocatalysts were introduced to the acrylic acid grafted membrane surface.

Song Yang; Jia-Shan Gu; Hai-Yin Yu; Jin Zhou; Shi-Feng Li; Xiu-Min Wu; Liang Wang

2011-01-01

119

Pervaporative dehydration of ethanol-water solution through asymmetric PC membrane surface modified via residual air plasma-induced graft polymerization of HEMA  

Microsoft Academic Search

This study investigated on the surface modification of an asymmetric polycarbonate (PC) membrane by means of exposure to residual air plasma followed by graft polymerization with 2-hydroxyethyl methacrylate (HEMA) monomer. A tubular type of an evacuated reactor was used in the plasma-induced surface pretreatment. Surface grafting was conducted in a temperature-controlled shaking water bath. The degree of grafting was calculated

Manuel De Guzman; Kueir-Rarn Lee; Juin-Yih Lai

2010-01-01

120

Radiation-induced grafting of vinyl benzyl trimethyl ammonium chloride onto nylon-6 fabric  

NASA Astrophysics Data System (ADS)

Vinyl benzyl trimethyl ammonium chloride (VBTAC) was grafted onto nylon-6 fabric in the presence of 2- hydroxy ethyl methacrylate (HEMA) by the simultaneous irradiation method in the presence of air with 60Co ?-radiations. An increase in grafting was observed with increasing dose. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) confirmed the grafting of VBTAC. Morphological changes after grafting were confirmed by scanning electron microscopy (SEM). The X-ray diffraction (XRD) pattern showed changes in crystallinity on grafting. The initial studies carried out with grafted nylon fabric showed behavioural changes in the burning properties.

Kolhe, Shailesh M.; Kumar, Ashok

2007-05-01

121

Study of radiation-induced grafting of 2-hydroxyethyl methacrylate to chloroprene rubber membrane  

NASA Astrophysics Data System (ADS)

The radiation-induced grafting copolymerization of HEMA to chloroprene rubber membranes were studied by means of irradiation of cobalt-60 gamma ray. The structure and surface morphology of both grafted and ungrafted CR membranes were observed by FT-IR-PAS spectroscopy and scanning electron microscope (SEM), respectively. The experimental results showed that the change of the degree of grafting in a mixed solvent of water and ethanol is S-shaped curve. The degree of grafting increases with increasing pH values in grafting solution. The influences of dose, dose rate, monomer concentration and grafting temperature were investigated. The degree of grafting does not change with increasing membrane thickness. This result showed that the grafting of HEMA to CR membrane is surface grafting.

Yue-E, Fang; Jun, Ji; Chaoxiong, Ma

1999-01-01

122

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption  

Microsoft Academic Search

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6Gy\\/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it

S. Benamer; M. Mahlous; D. Tahtat; A. Nacer-Khodja; M. Arabi; H. Lounici; N. Mameri

2011-01-01

123

Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl methacrylate onto chitosan  

NASA Astrophysics Data System (ADS)

In the present study, 2-hydroxyethyl methacrylate has been grafted onto chitosan by using either chemical initiation, or photo-induction or gamma radiation-induced polymerisation, all under heterogeneous conditions. The evidence of grafting was provided by Fourier transform infrared spectroscopy and thermal analysis. The results concerning the effect of initiator concentration, initial monomer concentration and dose rate influencing on the yield of grafting reactions are presented. These suggest that gamma irradiation is the method that leads to higher yields of grafting.

Casimiro, M. H.; Botelho, M. L.; Leal, J. P.; Gil, M. H.

2005-04-01

124

Crystal structure and mechanical properties of UHMWPE-g-PMA fiber prepared by radiation grafting  

NASA Astrophysics Data System (ADS)

Methyl acrylate (MA) monomer was grafted onto ultra-high molecular weight polyethylene (UHMWPE) fibers by ?-ray pre-irradiation induced graft polymerization. The grafting of MA on UHMWPE fiber was confirmed by thermogravimetric analysis and Fourier-transform infrared spectroscopy. The degree of grafting (DG) increased with an increase in absorbed dose and reached a significantly high value (approximately 200%) at 100 kGy. Scanning electron microscopy analysis revealed that the surface of the UHMWPE-g-PMA fibers was covered by the MA grafting layer and became rough. The monoclinic crystalline and orientated intermediate phases were disordered by the grafting chains such that degree of orientation declined gradually with increasing DG. The tensile strength of UHMWPE-g-PMA fiber decreased with increasing dose but was independent of DG, whereas the fiber modulus declined with DG. UHMWPE-g-PMA fiber that possesses desirable mechanical properties could be obtained at a dose of less than 10 kGy.

Xing, Zhe; Wang, Mouhua; liu, Weihua; Hu, Jiangtao; Wu, Guozhong

2013-05-01

125

Grafting polymerization of polyacetal onto nano-silica surface via bridging isocyanate  

Microsoft Academic Search

A method of surface modification of nano-silica by surface grafting of polyacetal (PAc) via bridging toluene 2,4-di-iso-cyanate (TDI) was developed. The resultant grafting rate of up to 79.6% was much higher than that of direct grafting of PAc. Monodisperse nano-silica in polar media was obtained under the optimal experimental condition. The sedimentation experiments showed that the modified nano-particles had good

Jianfei Che; Yinghong Xiao; Xin Wang; Anbo Pan; Wei Yuan; Xiaodong Wu

2007-01-01

126

Functionalization of cotton fabrics by radiation induced grafting of quaternary salt to impart antibacterial property  

NASA Astrophysics Data System (ADS)

High energy gamma radiation has been used to covalently link polymer chains of a quaternary ammonium salt containing monomer, viz. [2-(Acryloyloxyethyl)]trimethylammonium chloride (AETC) to cotton fabric by mutual radiation grafting using 2-hydroxyethyl methacrylate (2-HEMA) monomer as the grafting facilitator. Grafting yield was found to increase with the radiation dose and monomer concentration. The grafted samples have been characterized for water uptake, surface morphology and thermal stability and for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity particularly against gram-positive bacteria.

Goel, N. K.; Kumar, Virendra; Rao, M. S.; Bhardwaj, Y. K.; Sabharwal, S.

2011-11-01

127

Radiation-grafted, chemically modified membranes part I - Synthesis of a selective aluminum material  

NASA Astrophysics Data System (ADS)

Polymeric membranes were styrene grafted by irradiation methods and the obtained material was chemically modified to become aluminum selective. For this purpose, polymeric substrates of PVC (polyvinyl chloride) and PP (polypropylene) were styrene grafted mutually by gamma and electron beam irradiation. The modification process includes three basic reaction paths: Friedel-Crafts acylation, 2-methylanisole coupling and a final oxidation to achieve aluminum selectivity. Although this specific chemical modification in derivatives of polystyrene is not new, the new challenge is to obtain a selective material where original membrane characteristics (physical shape and mechanical resistance) are minimally conserved after such an aggressive treatment.

Bazante-Yamaguishi, Renata; Moura, Eduardo; Manzoli, José E.; Geraldo, Aurea B. C.

2014-01-01

128

Hydrophilic modification of polyethersulfone membranes by low temperature plasma-induced graft polymerization  

Microsoft Academic Search

A complete and permanent hydrophilic modification of polyethersulfone (PES) membranes is achieved by argon plasma treatment followed by polyacrylic acid (PAA) grafting in vapor phase. Both Ar plasma treatment alone and post-PAA grafting rendered a complete hydrophilicity to the PES membranes. The hydrophilicity of the membranes treated with only the Ar plasmas is not, however, permanent. In contrast, the PES

Dattatray S Wavhal; Ellen R Fisher

2002-01-01

129

Investigations and characterization of radiation grafted copolymers for possible practical use in waste water treatment  

NASA Astrophysics Data System (ADS)

Selective removal and recovery of metals from industrial effluent is an environmental problem and economic concern. There are a number of heavy metals that are candidates for removal prior to having waste solutions coming in contact with the environment. Therefore, a study has been made on the preparation of hydrophilic membranes having both anionic and cationic exchangers. To achieve such properties in the required membranes, a trial has been made on the radiation graft copolymerization of binary monomers possessing anionic and cationic exchangers such as acrylic acid/2- and 4-vinyl pyridine (AAc/2-VP) (AAc/4-VP) onto available commercial polymeric substrate such as low-density polyethylene (LDPE). The preparation conditions at which the grafting process proceeds homogeneously are determined. Characterization and some selected properties of the prepared grafted membranes were studied and accordingly the possibility of its practicable use in waste water treatment from heavy and toxic metals such as Pb, Zn, Cd, Fe,… etc. was investigated. The metal uptake by such prepared membranes was determined by using atomic absorption technique. The membrane efficiency and durability was investigated. The maximum uptake for a given metal was higher for the LDPE-g-P (AAc/2VP) membranes than that for the LDPE-g-P (AAc/4VP). The chelated metal ions were easily desorbed by treating the membrane with 0.1 N HCl for 2 h at room temperature. A mixture of two or three metals in the same feed solution was used to determine the selectivity of the membrane towards different metals. The results obtained for the prepared membranes showed a great promise for their applicability in the removal of heavy metals from wastewater.

Hegazy, El-Sayed A.; El-Rehim, H. A. Abd; Shawky, H. A.

2000-01-01

130

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.  

PubMed

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy. PMID:15620338

Yu, W H; Kang, E T; Neoh, K G

2005-01-01

131

Radiation grafting of methyl methacrylate onto polyethylene separators for lithium secondary batteries  

NASA Astrophysics Data System (ADS)

Micro-porous polyethylene separator was modified by radiation grafting of methyl methacrylate in order to improve its affinity with a liquid electrolyte. The degree of grafting (DOG) increased with the monomer concentration and grafting time. The morphological change of the modified separator was investigated by scanning electron microscopy. The degree of crystallinity upon grafting was reduced due to the formation of an amorphous PMMA layer. The electrolyte uptake and the ionic conductivity of the separator increased with an increase in the DOG. The ionic conductivity reached 2.0 mS/cm for the grafted polyethylene separator with 127 wt% DOG.

Gwon, Sung-Jin; Choi, Jae-Hak; Sohn, Joon-Yong; An, Sung-Jun; Ihm, Young-Eon; Nho, Young-Chang

2008-08-01

132

Double plasma treatment-induced graft polymerization of carbohydrated monomers on poly(ethylene terephthalate) fibers.  

PubMed

This study deals with the grafting of carbohydrate monomers on poly(ethylene terephthalate) fibers by double argon plasma treatment. Two monomers were used: allyl alpha-D-galactopyranoside and 2-methacryloxyethyl glucoside. The quantity of grafted carbohydrates was determined by phenol/sulfuric acid colorimetric titration. The graft density was observed to vary according to the monomer used. Allyl alpha-D-galactopyranoside yields to smaller graft densities compared to 2-methacryloxyethyl glucoside, suggesting transfer reactions occurring at the surface with allyl alpha-D-galactopyranoside. Fibers with the highest graft levels were obtained with the higher monomer concentration and the lower quantity of fiber treated in a plasma reactor. The grafting density can be modulated by the monomer concentration and mass of fiber exposed in the plasma reactor. For 0.5 mg of fibers, the graft densities for 23 and 68 mM allyl alpha-D-galactopyranoside are, respectively, 18 and 35 nmol/cm2. For 0.5 mg of fibers, the graft densities for 19 and 38 mM 2-methacryloxyethyl glucoside are, respectively, 150 and 250 nmol/cm2. Comparative study without the preactivation treatment shows the efficiency of the preactivation: for a mass of fiber of 0.5 mg and a 2-methacryloxyethyl glucoside concentration of 38 mM, the grafting density without plasma pretreatment is 38 nmol/cm2. Attenuated total reflectance Fourier transform infrared spectra confirmed the anchoring of the glycopolymer onto the poly(ethylene terephthalate) surfaces. Atomic force microscopy and scanning electronic microscopy pictures indicated their morphological changes. PMID:17711314

Bech, Loïc; Lepoittevin, Bénédicte; El Achhab, Abdelhakim; Lepleux, Emmanuel; Teulé-Gay, Lionel; Boisse-Laporte, Caroline; Roger, Philippe

2007-09-25

133

Thermo-responsive wound dressings by grafting chitosan and poly(N-isopropylacrylamide) to plasma-induced graft polymerization modified non-woven fabrics  

NASA Astrophysics Data System (ADS)

To obtain a chitosan wound dressings with temperature-responsive characteristics, polypropylene (PP) non-woven fabric (NWF) was modified by direct current pulsed oxygen plasma-induced grafting polymerization of acrylic acid (AAc) to improve hydrophilicity and to introduce carboxylic acid groups. Conjugation of chitosan and poly(N-isopropylacrylamide) (PNIPAAm) followed by using water-soluble carbodiimide as a coupling agent to form a novel bigraft PP-g-chitosan-g-PNIPAAm wound dressing. The amount of chitosan and PNIPAAm grafted to PP-g-chitosan-g-PNIPAAm were 83.0 ± 4.6 ?g/cm2 and 189.5 ± 8.2 ?g/cm2, respectively. The surface chemical composition and microstructure of the NWF were studied by electron spectroscopy for chemical analysis (ESCA) and scanning electron microscopy (SEM). The linkages between AAc, chitosan, and PNIPAAm were confirmed with the formation of amide bonds. Physical properties of the NWF were characterized and potentials of these NWFs as wound dressings were evaluated using SD rat as the animal model. NWFs contained PNIPAAm were better than those contained only chitosan in wound healing rates and the wound areas covered by PP-g-chitosan-g-PNIPAAm wound dressings healed completely in 17 days.

Chen, Jyh-Ping; Kuo, Chang-Yi; Lee, Wen-Li

2012-12-01

134

Grafting.  

PubMed

Grafting provides a simple way to generate chimeric plants with regions of different genotypes, and thus to assess the cell autonomy of gene action. The technique of grafting has been widely used in other species, but in Arabidopsis, its small size makes the process rather more complicated. However, there are now several well-established grafting procedures available, which we described here, and their use has already contributed greatly to understanding of such processes as shoot branching control, flowering, and disease resistance. PMID:16739566

Bainbridge, Katherine; Bennett, Tom; Turnbull, Colin; Leyser, Ottoline

2006-01-01

135

Novel Diblock Copolymer-Grafted Multiwalled Carbon Nanotubes via a combination of Living and Controlled/Living Surface Polymerizations  

SciTech Connect

Diels Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1-benzocylcobutene-10-phenylethylene (BCB-PE) or 4-hydroxyethylbenzocyclobutene (BCB-EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and e-caprolactone (e-CL), respectively. The OH-end groups were transformed to isopropylbromide groups by reaction with 2-bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2-dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Mays, Jimmy [University of Tennessee, Knoxville (UTK); Hadjichristidis, Nikos [University of Athens, Athens, Greece

2010-01-01

136

Study on radiation-induced grafting of styrene onto chitin and chitosan  

NASA Astrophysics Data System (ADS)

Radiation-induced grafting of styrene onto chitin and chitosan powder was performed at room temperature. The effect of various conditions such as absorbed dose, solvent and oxygen on grafting was investigated. The grafting yield increased with the increase in absorbed dose. At the same dose, the grafting yield of styrene on chitosan was higher than that on chitin. The grafting reaction was promoted in the presence of methanol, and oxygen delayed the grafting reaction but did not inhibit it completely. In order to study the mechanism of grafting reaction and analyze the grafted samples, the grafted products were extracted first by benzene, then they were hydrolyzed in the presence of acid and separated by thin layer chromatography (TLC). Three different kinds of polystyrene (PS), i.e. PS grafted onto chitin, PS embedded in chitin and PS in grafting solution were gained. The variation of their molecular weight (MW) and width index of molecular weight distribution ( Mw/ Mn) determined by gel permeation chromatography (GPC) at different grafting conditions is discussed.

Pengfei, Liu; Maolin, Zhai; Jilan, Wu

2001-05-01

137

Radiation-induced polymerization for the immobilization of penicillin acylase  

SciTech Connect

The immobilization of Escherichia coli penicillin acylase was investigated by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperature. A leak-proof composite that does not swell in water was obtained by adding the cross-linking agent trimethylolpropane trimethacrylate to the monomer-aqueous enzyme mixture. Penicillin acylase, which was immobilized with greater than 70% yield, possessed a higher Km value toward the substrate 6-nitro-3-phenylacetamidobenzoic acid than the free enzyme form (Km = 1.7 X 10(-5) and 1 X 10(-5) M, respectively). The structural stability of immobilized penicillin acylase, as assessed by heat, guanidinium chloride, and pH denaturation profiles, was very similar to that of the free-enzyme form, thus suggesting that penicillin acylase was entrapped in its native state into aqueous free spaces of the polymer matrix.

Boccu, E.; Carenza, M.; Lora, S.; Palma, G.; Veronese, F.M.

1987-06-01

138

Stabilization of alginate beads using radiation polymerized polyacrylamide.  

PubMed

A technique has been described for the stabilization of calcium alginate beads using radiation polymerized acrylamide. The technique involved dropping a mixture containing the cells (20%), sodium alginate (2%), acrylamide (2.5%) and N-N'-methylene-bis-acrylamide (0.1%) through a syringe needle into cold (-75 degrees C) toluene. The frozen beads obtained were exposed to 60Co gamma-rays (0.5 KGy) and were then thawed in 0.1 M CaCl2 solution. Unlike the calcium alginate beads the conjugate beads were not found to be dissolved when incubated in 3% trisodium citrate solution. Stabilized beads containing entrapped yeast cells could be reused for over 15 batches for the inversion of sucrose without loss in activity or chemical integrity of the beads. PMID:10481950

Gupte, A; D'Souza, S F

1999-07-28

139

Synthesis and Characterization of Block-Graft Copolymers [poly(epichlorohydrin- b -styrene)- g -poly(methyl methacrylate)] by Combination of Activated Monomer Polymerization, NMP and ATRP  

Microsoft Academic Search

Summary  Synthesis of block-graft copolymers, namely poly(epichlorohydrin-b-styrene)-g-poly(methyl methacrylate) (PECH-b-St)-g-PMMA) by combination of Activated Monomer (AM), Nitroxide Mediated Polymerization (NMP) and Atom Transfer Radical Polymerization\\u000a (ATRP) methods was described. For this purpose, first epichlorohydrin (ECH) was polymerized by using BF3THF complex in the presence of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyl-1-oxy (HTEMPO) via AM mechanism. The resulting\\u000a stable radical terminated polymer was subsequently used as a counter

M. Atilla Tasdelen; Yusuf Yagci; A. Levent Demirel; Tadeusz Biedron; Przemyslaw Kubisa

2007-01-01

140

Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl methacrylate onto chitosan  

Microsoft Academic Search

In the present study, 2-hydroxyethyl methacrylate has been grafted onto chitosan by using either chemical initiation, or photo-induction or gamma radiation-induced polymerisation, all under heterogeneous conditions. The evidence of grafting was provided by Fourier transform infrared spectroscopy and thermal analysis.The results concerning the effect of initiator concentration, initial monomer concentration and dose rate influencing on the yield of grafting reactions

M. H. Casimiro; M. L. Botelho; J. P. Leal; M. H. Gil

2005-01-01

141

Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl methacrylate onto chitosan  

Microsoft Academic Search

In the present study, 2-hydroxyethyl methacrylate has been grafted onto chitosan by using either chemical initiation, or photo-induction or gamma radiation-induced polymerisation, all under heterogeneous conditions. The evidence of grafting was provided by Fourier transform infrared spectroscopy and thermal analysis. The results concerning the effect of initiator concentration, initial monomer concentration and dose rate influencing on the yield of grafting

M. H. Casimiro; M. L. Botelho; J. P. Leal; M. H. Gil

2005-01-01

142

Grafting of poly(ethylene glycol) monoacrylates on polycarbonateurethane by UV initiated polymerization for improving hemocompatibility.  

PubMed

Poly(ethylene glycol) monoacrylates (PEGMAs) with a molecular weight between 400 and 1,000 g mol(-1) were grafted by ultraviolet initiated photopolymerization on the surface of polycarbonateurethane (PCU) for increasing its hydrophilicity and improving its hemocompatibility. The surface-grafted PCU films were characterized by Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle, scanning electron microscopy (SEM) and atomic force microscopy measurements. The surface properties of the modified films were studied in dry and wetted state. Blood compatibility of the surfaces was evaluated by platelet adhesion tests and adhered platelets were determined by SEM. The results showed that the hydrophilicity of the films had been increased significantly by grafting PEGMAs, and platelets adhesion onto the film surface was obviously suppressed. Furthermore, the molecular weight of PEGMAs had a great effect on the hydrophilicity and hemocompatibility of the PCU films after surface modification and increased with increasing molecular weight of PEGMAs. PMID:22661245

Feng, Yakai; Zhao, Haiyang; Behl, Marc; Lendlein, Andreas; Guo, Jintang; Yang, Dazhi

2013-01-01

143

In vitro release studies of vitamin B 12 from poly N-vinyl pyrrolidone/starch hydrogels grafted with acrylic acid synthesized by gamma radiation  

NASA Astrophysics Data System (ADS)

Co-polymeric hydrogels containing N-vinyl pyrrolidone and starch grafted with acrylic acid were synthesized by gamma radiation to be used as drug delivery system. Their gel contents, grafting swelling and thermal gravimetric analysis were evaluated. The gel content increases by increasing the irradiation dose up to 50 kGy, then decreases. The grafting percent increases by the increasing of acrylic acid. The thermal stability and the rate of the thermal decomposition changed according to the different compositions. The maximum rate of the thermal decomposition decreases by increasing the irradiation dose from 20 to 30 kGy and increases by increasing the irradiation dose from 30 to 70 kGy. The hydrogels loaded with vitamin B 12 demonstrated a decrease release in acidic medium than the neutral one.

Eid, M.

2008-12-01

144

Current status of adsorbent for metal ions with radiation grafting and crosslinking techniques  

Microsoft Academic Search

Removal of toxic metals from streaming water and ground water is important task to preserve environment. Radiation processing of grafting and crosslinking can synthesis adsorbent having high performances. Graft adsorbent can be synthesized by using the conventional polymer like polyethylene having variety shapes such as membrane, cloth, and fiber. Especially, the obtained fibrous adsorbent has 100 times higher rate of

Noriaki Seko; Masao Tamada; Fumio Yoshii

2005-01-01

145

Radiation Grafting of Acrylonitrile onto Polyester Fiber as the Reinforcing Filler for Poly (Vinyl Chloride).  

National Technical Information Service (NTIS)

Studies have been carried out on radiation-induced grafting of acrylonitrile onto polyester fiber and on the properties of the grafted fiber in an attempt to increase the strength of polyester fiber reinforced soft poly (vinyl chloride) (PVC) sheet by imp...

K. Kaji I. Ando

1985-01-01

146

Functionalization of nanochannels by radio-induced grafting polymerization on PET track-etched membranes  

NASA Astrophysics Data System (ADS)

The application of swift-heavy ion bombardment to polymers is a well-established technique to manufacture micro- and nanopores onto polymeric films to obtain porous membranes. A few years ago, it was realized that, during ion bombardment, the high energy deposition along the ion path through the polymer reached cylindrical damage regions corresponding to the core trace and the penumbra. After the etching procedure, there are still enough active sites left in the penumbra that can be used to initiate a polymerization process selectively inside the membrane pores.

Soto Espinoza, S. L.; Arbeitman, C. R.; Clochard, M. C.; Grasselli, M.

2014-01-01

147

Effect of Far-infrared Radiation on Thermal Cationic Polymerization of Epoxy Resin  

Microsoft Academic Search

The effect of far-infrared radiation on cationic polymerization of epoxy resin was studied by thermal quantitative analysis. We use titanium oxide and aluminium oxide as ceramics for low temperature radiation. The absorption spectrum of epoxy resin depicts far infrared absorption from 6.6 to 16 mum. The radiation intensity spectrum of these ceramics were measured using black body standard. Radiation intensity

Shin Kiyokawa; Yasumasa Morita; Haruo Inoue; Haruo Hirose; Noboru Morita; Toshitsugu Hara

2004-01-01

148

Stearyl methacrylate-grafted-chitosan nanoparticle as a nanofiller for PLA: Radiation-induced grafting and characterization  

NASA Astrophysics Data System (ADS)

This paper reports a one-pot synthesis using radiation-induced grafting technique to modify biopolymer-based chitosan nanoparticles as a nanofiller for blending with poly(lactic acid) (PLA). Hydrophobic stearyl methacrylate (SMA) was grafted onto non-irradiated chitosan (CS0) and pre-irradiated chitosan with a ?-ray dose of 40 kGy (CS40) to obtain stearyl methacrylate-grafted-chitosan nanoparticles (SMA-g-CSNPs).The effects of the pre-irradiated CS, grafting doses and SMA concentrations on degree of grafting (DG) and particle formation were studied. FT-IR and XRD were used to characterize the chemical and packing structure of SMA-g-CSNPs. The particle formulation and size of SMA-g-CSNPs were observed by TEM and AFM. The spherical core-shell SMA-g-CSNPs with the size ranging from 50 to 140 nm were successfully prepared. The SMA-g-CSNPs from CS40 has higher DG and smaller particle size when compared with CS0. The SMA-g-CSNPs are able to improve the compatibility between CS and PLA.

Rattanawongwiboon, Thitirat; Haema, Kamonwon; Pasanphan, Wanvimol

2014-01-01

149

Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification  

NASA Astrophysics Data System (ADS)

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.

Wada, Yuki; Seko, Noriaki; Nagasawa, Naotsugu; Tamada, Masao; Kasuya, Ken-ichi; Mitomo, Hiroshi

2007-06-01

150

Surface modification of poly(ether ether ketone) with methacryloyl-functionalized phospholipid polymers via self-initiation graft polymerization.  

PubMed

To improve blood compatibility of poly(ether ether ketone) (PEEK), surface modification with methacryloyl-functionalized phospholipid polymers was performed through self-initiation graft polymerization. The copolymers (PMA) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride were synthesized by conventional free radical polymerization. The PMA was then immobilized with pentafluorophenyl methacrylate to obtain methacryloyl-functionalized MPC polymers (PMAMA). The degree of substitution of the methacryloyl group into the copolymer was nearly completed. The PMAMA was dissolved in 1-butanol and the solution was dropped on PEEK. UV light (350?±?50?nm) was subsequently irradiated on PEEK for various periods. Elemental analysis of the PEEK surface was performed by X-ray photoelectron spectroscopy and phosphorus and nitrogen signals due to the MPC units on PEEK were observed. The surface wettability of PEEK was also improved by immobilization of PMAMA. Plasma protein adsorption was effectively reduced on the PMAMA-immobilized surface regardless of the type of protein. Furthermore, PMAMA immobilization was also useful in reducing platelet adhesion on PEEK. In conclusion, methacryloyl-functionalized MPC polymers could be immobilized on PEEK by simple photo-irradiation, resulting in significant improvement in blood compatibility. PMID:24766535

Kawasaki, Yoshihiro; Iwasaki, Yasuhiko

2014-06-01

151

Significance of radiation grafting in curing processes: Role of additives in these reactions  

NASA Astrophysics Data System (ADS)

The importance of observing concurrent grafting with curing in polymerisation processes initiated by UV and ionising radiation is discussed. Methyl methacrylate (MMA) is used as monomer with cellulose and polypropylene (PPE) as backbone polymers in the model grafting system studied. The styrene comonomer technique is utilised to overcome homopolymerisation in these reactions. The effect of typical materials used in curing processes as additives in grafting has been examined. The additives used include mineral acids, photoinitiators, thermal initiators, a typical inclusion compound like urea and polyfunctional monomers especially the multifunctional acrylates and methacrylates. A representative commercial curing process where these grafting concepts are relevant is discussed in detail. The process chosen for illustration is the UV cured banknote, a world first. A theory to explain the observed reactivity in grafting and curing is proposed involving physical and chemical processes which act in concert. The physical process involves partitioning of reagents whereas the chemical process concerns additional radical reactions in the radiation initiation step.

Garnett, John L.; Ng, Loo-Teck; Viengkhou, Visay

152

Functionalization of polymer surfaces by radiation-induced grafting for separation of heavy metal ions  

NASA Astrophysics Data System (ADS)

The reported investigations were focused on the elucidation of the most important factors influencing radiation-induced grafting, particularly on studying the relationship between layer structure formed via copolymerization and content of monomers in the initial solution. Sorption capacity of the prepared by radiation grafting adsorber was evaluated by gamma radiometer using 152Eu3+ as a marker monitoring depletion of the radioisotope from the feed solution.

Kornacka, E. M.; Przybytniak, G.; Fuks, L.; Walo, M.; ?yczko, K.

2014-01-01

153

Polyethylene glycol-grafted poly-L-lysine as polymeric gene carrier.  

PubMed

A new series of gene carriers, polyethylene glycol (PEG)-grafted poly-L-lysine (PLL, mol. wt. = 25000) with three different PEG-grafted ratios (5, 10 and 25 mole%, which means 5, 10 and 25% of epsilon-amino group of PLL was modified by PEG), was synthesized. These new gene carriers, named comb-shaped PEG-g-PLL copolymer, showed a 5- to 30-fold increase in transfection efficiency compared to PLL alone on a human carcinoma cell line. It is likely that Hep G2 cells were transfected by plasmid DNA/PEG-g-PLL complexes through an endocytosis mechanism due to the fact that chloroquine increased transfection efficiency. Although Lipofectin, a cationic lipid formulation, showed slightly higher transfection efficiency than PEG-g-PLL in Hep G2 cells, our designed PEG-g-PLL demonstrated lower cytotoxicity, early gene expression and maintenance of gene expression for up to 96 h. PMID:9741902

Choi, Y H; Liu, F; Kim, J S; Choi, Y K; Park, J S; Kim, S W

1998-06-01

154

Graft polymerization of guar gum with acryl amide irradiated by microwaves for colonic drug delivery.  

PubMed

This article is aimed to discuss the modification of guar gum through microwave irradiation by varying the time of irradiation. The characterization of the modified products was carried out using FTIR spectroscopic analysis. The FT-IR spectrum of the pure guar gum (GG) sample showed a broad peak at 3298 cm(-1) while the modified GG sample displayed a peak at 1541 cm(-1) which was absent in the crude sample. The X-ray diffraction (XRD) analysis confirmed the increase in crystallinity due to grafting of the sample with polyacrylamide (GG-g-PAM). Scanning electron microscope (SEM) images revealed that granular form of guar gum was changed into fibrillar structure after grafting. Thermo-gravimetric analysis of the modified samples was also carried out and discussed. The role of guar gum as a matrix for controlled release of drug triamcinolone was evaluated. The GG-acrylamide grafted samples presented a correlation between drug release and time of microwave exposure. The results revealed that such modified product has potential applications in colonic drug delivery system. PMID:23973495

Shahid, Muhammad; Bukhari, Shazia Anwer; Gul, Yousra; Munir, Hira; Anjum, Fozia; Zuber, Mohammad; Jamil, Tahir; Zia, Khalid Mahmood

2013-11-01

155

Mechanical properties of radiation-sterilised human Bone-Tendon-Bone grafts preserved by different methods.  

PubMed

Patellar tendon auto- and allo-grafts are commonly used in orthopedic surgery for reconstruction of the anterior cruciate ligaments (ACL). Autografts are mainly used for primary reconstruction, while allografts are useful for revision surgery. To avoid the risk of infectious disease transmission allografts should be radiation-sterilised. As radiation-sterilisation supposedly decreases the mechanical strength of tendon it is important to establish methods of allograft preservation and sterilisation assuring the best quality of grafts and their safety at the same time. Therefore, the purpose of this study was to compare the tensile strength of human patellar tendon (cut out as for ACL reconstruction), preserved by various methods (deep fresh freezing, glycerolisation, lyophilisation) and subsequently radiation-sterilised with doses of 0, 25, 50 or 100 kGy. Bone-Tendon-Bone grafts (BTB) were prepared from cadaveric human patella tendons with both patellar and tibial attachments. BTB grafts were preserved by deep freezing, glycerolisation or lyophilisation and were subsequently radiation-sterilised with doses of 0 (control), 25, 50 or 100 kGy. All samples were subjected to mechanical failure tensile tests with the use of Instron system in order to estimate their mechanical properties. All lyophilised grafts were rehydrated before performing of those tests. Obtained mechanical tests results of examined grafts suggest that deep-frozen irradiated grafts retain their initial mechanical properties to an extent which does not exclude their clinical application. PMID:18982427

Kami?ski, A; Gut, G; Marowska, J; Lada-Koz?owska, M; Biwejnis, W; Zasacka, M

2009-08-01

156

Preparation of core–shell structured T-ZnOw\\/polyaniline composites via graft polymerization  

Microsoft Academic Search

The tetra-needle like zinc oxide whisker (T-ZnOw) was treated with ?-aminopropyltriethoxysilane (APTS), a coupling agent of silane with amino-group, to form a protection and bonding layer on its surface, where polyaniline (PANI) was in situ polymerized to form a new kind of core–shell structured T-ZnOw\\/PANI composites. The structure, morphologies, and conductivity of the synthesized products were characterized by Fourier transform

Xiaolang Chen; Zuowan Zhou; Wangchun Lv; Ting Huang; Shuchun Hu

2009-01-01

157

Preparation of polysulfone nanofiltration membranes by UV-assisted grafting polymerization for water softening  

Microsoft Academic Search

The rising demand for high quality water heightens the need to soften hard and very hard water. In this study, flat sheet polysulfone ultrafiltration membranes were prepared by phase inversion and modified by UV-induced polymerization of acrylic acid in order to prepare nanofiltration membranes for water desalination. Polyethylene glycol of different molecular weights mainly in the range of 1500–4000Da were

Maryam Homayoonfal; Ahmad Akbari; Mohammad Reza Mehrnia

2010-01-01

158

Rubber products prepared from silica modified by radiation-induced admicellar polymerization  

NASA Astrophysics Data System (ADS)

Unmodified silica, silica modified with Si69, silica modified by thermal admicellar polymerization and silica modified by radiation-induced admicellar polymerization were applied as rubber reinforcement. Mechanical properties of these different rubber formulae were subsequently tested. The results revealed that the mechanical properties of rubber reinforced with silica modified by admicellar polymerization were superior to those reinforced with unmodified silica or silica modified with Si69. As for the silica modified by admicellar polymerization, cetyltrimethyl ammonium bromide (CTAB) proved to be the most effective surfactant, compared to dodecyltrimethyl ammonium bromide (DTAB) and tetradecyltrimethyl ammonium bromide (TTAB).

Pongprayoon, Thirawudh; Yooprasert, Narissara; Suwanmala, Phiriyatorn; Hemvichian, Kasinee

2012-05-01

159

Preparation of poly( N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography  

NASA Astrophysics Data System (ADS)

Thermoresponsive poly( N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyratefunctionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl2/ N,N,N',N',N?-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/ m2 and 0.0215 chains/nm2, respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution ( M w/ M n= 1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.

Liu, Zong-Jian; Liang, Yan-Li; Geng, Fang-Fang; Lv, Fang; Dai, Rong-Ji; Zhang, Yu-Kui; Deng, Yu-Lin

2012-03-01

160

Utilization of gamma Radiation to Enhance the Properties of Polymers and to Initiate Polymerization of Monomers.  

National Technical Information Service (NTIS)

Preliminary studies to develop capability in the use of gamma radiation to induce polymerization have been completed. Some attempts to produce polymers from some monomers are now underway. Results and future plans are discussed. (Author)

G. Hargreaves

1965-01-01

161

Gamma radiation-induced grafting of acrylamide and dimethyl diallyl ammonium chloride onto starch.  

PubMed

Corn starch graft copolymers were prepared from acrylamide/dimethyl diallyl ammonium chloride binary monomers (AM/DMDAAC) by a simultaneous radiation grafting method, and were characterized by FTIR and (1)H NMR techniques, weight measurement and titration method. The copolymers with high grafting ratio and high grafting efficiency of binary monomers were achieved at absorbed doses of 2 kGy and 3 kGy using a 6:9.8:4.2 (w/w/w) ratio of starch/AM/DMDAAC, but their cationic degrees were low. Grafting ratio, grafting efficiency and cationic degree of the copolymers increased with increasing AM content in comonomer mixtures and then decreased at 3kGy using a 6:14 ratio of starch:total comonomers, but their cationic degrees generally decreased with increasing AM content. The grafting ratio, the grafting efficiency and the cationic degree of the copolymers increased, but the grafting efficiency of DMDAAC decreased with varying starch/(AM+DMDAAC) ratio from 6:3 to 6:18 at 3 kGy by using a fixed 7:3 ratio of AM:DMDAAC. PMID:23218310

Lv, Xiaohua; Song, Weiqiang; Ti, Yongzhou; Qu, Lingbo; Zhao, Zhiwei; Zheng, Hongjuan

2013-01-30

162

Fire Proofing by Radiation Grafting (Application on Polyester and Polypropylene).  

National Technical Information Service (NTIS)

This report outlines efforts to try out a modern technique, 'radition grafting', rather than chemical and heat fixation, to make textiles more fire-proof by reducing as much as possible the deterioration in conventional properties, in particular softness ...

B. J. Hill U. Einsele G. Di Modica D. Wattiez

1980-01-01

163

Effect of Far-infrared Radiation on Thermal Cationic Polymerization of Epoxy Resin  

NASA Astrophysics Data System (ADS)

The effect of far-infrared radiation on cationic polymerization of epoxy resin was studied by thermal quantitative analysis. We use titanium oxide and aluminium oxide as ceramics for low temperature radiation. The absorption spectrum of epoxy resin depicts far infrared absorption from 6.6 to 16 ?m. The radiation intensity spectrum of these ceramics were measured using black body standard. Radiation intensity absorbed by epoxy resin was much higher at aluminium oxide than titanium oxide. We performed cationic polymerization of epoxy resin and monitored thermal input and output by differential scanning calorimetry (DSC) using a ceramics coated DSC aluminium pan. Reaction initiation and termination temperatures of polymerization were nearly the same with or without ceramics. The reaction rate was maximal with aluminium oxide, however. We also tested polymerization of epoxy resin after mixing with 1% w/v of ceramics. The relative proportions of aluminium oxide and titanium oxide were varied. DSC measurements showed that the reaction energy of polymerization decreased after addition of ceramic. The decline was more pronounced with increasing aluminum oxide concentrations. For practical application of far-infrared radiation to epoxy resin polymerization, we studied LED encapsulation.

Kiyokawa, Shin; Morita, Yasumasa; Inoue, Haruo; Hirose, Haruo; Morita, Noboru; Hara, Toshitsugu

164

New Applications of Ring-Opening Metathesis Polymerization for Grafting Alkylene Oxide-Based Copolymers  

NASA Astrophysics Data System (ADS)

This research tackles the challenges of innovative modification of poly(allyl alkylene oxides) by ROMP to produce new materials. Firstly, binary and ternary copolymers, poly(epichlorohydrin-allyl glycidyl ether) (ECH-AGE) and poly (epichlorohydrin-propylene oxide-allyl glycidyl ether) (ECH-PO-AGE), have been prepared using as initiator a catalytic system consisting of an alkyl aluminium, controlled amounts of water and different compounds (ethers, diols, phosphines, salicylic acid derivatives, organozincs) acting as cocatalysts. Among catalysts explored in these copolymerizations most productive showed to be the systems triisobutylaluminium (TIBA), water and Zn(DIPS)2 or Zn(acac)2. Copolymers which have become thus available were subsequently grafted onto the pendent allylic groups by ROMP with cycloolefins (cyclooctene, norbornene, cyclododecene) involving ruthenium based catalysts.

Spurcaciu, Bogdan; Buzdugan, Emil; Nicolae, Cristian; Ghioca, Paul; Iancu, Lorena; Dragutan, Valerian; Dragutan, Ileana

165

Effect of Solvents on Gamma Radiation–Induced Graft Copolymerization of Vinyl Acetate onto Poly(3-hydroxybutyrate)  

Microsoft Academic Search

The effect of different solvents on the radiation-induced graft copolymerization of vinyl acetate onto poly(3-hydroxybutyrate) was studied. Structures of copolymers were determined with the techniques of thermogravimetric analysis and differential scanning calorimetry. From the thermal analysis results, it was found that the more favorable solvent to be used in the graft reaction is hexane. However, a much higher grafting degree

Maykel González; Pedro Ortíz; Manuel Rapado; Norma Galego

2009-01-01

166

Photo-bromination and photo-induced graft polymerization as a two-step approach for surface modification of polyacrylonitrile ultrafiltration membranes  

Microsoft Academic Search

A two-step heterogeneous polymer surface modification was developed, involving photo-bromination as activation and subsequent UV-induced graft polymerization with acrylic monomers. With polyacrylonitrile (PAN) ultrafiltration (UF) membranes, extent and effects of photo-bromination compared with the thermal reaction were studied with gravimetry, diffuse reflectance UV and ATR-IR spectroscopy, and scanning electron microscopy (SEM) as well as the UF properties. The yields of

Mathias Ulbricht; Annett Oechel

1996-01-01

167

Localized Surface Plasmon Resonance Nanosensing of C-Reactive Protein with Poly(2-methacryloyloxyethyl phosphorylcholine)-Grafted Gold Nanoparticles Prepared by Surface-Initiated Atom Transfer Radical Polymerization.  

PubMed

Highly sensitive and selective protein nanosensing based on localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) on which polymerized specific ligands were grafted as an artificial protein recognition layer for the target protein were demonstrated. As a model, optical nanosensing for C-reactive protein (CRP), a known biomarker for chronic inflammation that predicts the risk of arteriosclerosis or heart attacks, was achieved by measuring the shift of LSPR spectra derived from the change of permittivity of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted AuNPs (PMPC-g-AuNPs) upon interacting with CRP, in which the PMPC-g-AuNPs layer were grafted on AuNPs by surface-initiated atom transfer radical polymerization (ATRP). This nanosensing system was effective even for detecting CRP concentrations in a human serum solution diluted to 1% (w/w), at which point a limit of detection was ?50 ng/mL and nonspecific adsorption of other proteins was negligible. The nanosensing system using specific ligand-grafted AuNPs has several strengths, such as low preparation cost, avoiding the need for expensive instruments, no necessary complex pretreatments, and high stability, because it does not contain biobased molecules. We believe this novel synthetic route for protein nanosensors, composed of AuNPs and a polymerized specific ligand utilizing surface-initiated controlled/living radical polymerization, will provide a foundation for the design and synthesis of nanosensors targeting various other biomarker proteins, paving the way for future advances in the field of biosensing. PMID:24830565

Kitayama, Yukiya; Takeuchi, Toshifumi

2014-06-01

168

Radiation-induced eco-compatible sulfonated starch\\/acrylic acid graft copolymers for sucrose hydrolysis  

Microsoft Academic Search

Radiation-induced graft-copolymers capable of hosting sulfonic groups and having more effective catalytic activity towards sucrose hydrolysis were prepared. Acrylic acid monomer (AA) was copolymerized with sulfonated starch (SS) at different compositions using ionizing radiation. Swelling behavior of the prepared copolymers at different environmental conditions was studied as well as thermal stability. The hydrolysis of sucrose to glucose and fructose by

H. A. Abd El-Rehim; D. A. Diaa

169

Characterization of Bonding Between Poly(dimethylsiloxane) and Cyclic Olefin Coplymer Using Corona Discharge Induced Grafting Polymerization  

PubMed Central

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated.

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z. Hugh

2011-01-01

170

Characterization of bonding between poly(dimethylsiloxane) and cyclic olefin copolymer using corona discharge induced grafting polymerization.  

PubMed

Thermoplastics have been increasingly used for fabricating microfluidic devices because of their low cost, mechanical/biocompatible attributes, and well-established manufacturing processes. However, there is sometimes a need to integrate such a device with components made from other materials such as polydimethylsiloxane (PDMS). Bonding thermoplastics with PDMS to produce hybrid devices is not straightforward. We have reported our method to modify the surface property of a cyclic olefin copolymer (COC) substrate by using corona discharge and grafting polymerization of 3-(trimethoxysilyl)propyl methacrylate; the modified surface enabled strong bonding of COC with PDMS. In this paper, we report our studies on the surface modification mechanism using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement. Using this bonding method, we fabricated a three-layer (COC/PDMS/COC) hybrid device consisting of elastomer-based valve arrays. The microvalve operation was confirmed through the displacement of a dye solution in a fluidic channel when the elastomer membrane was pneumatically actuated. Valve-enabled microfluidic handling was demonstrated. PMID:21962541

Liu, Ke; Gu, Pan; Hamaker, Kiri; Fan, Z Hugh

2012-01-01

171

An efficient approach to obtaining water-compatible and stimuli-responsive molecularly imprinted polymers by the facile surface-grafting of functional polymer brushes via RAFT polymerization.  

PubMed

A new and efficient approach to obtaining molecularly imprinted polymers (MIPs) with both pure water-compatible (i.e., applicable in the pure aqueous environments) and stimuli-responsive binding properties is described, whose proof-of-principle is demonstrated by the facile modification of the preformed MIP microspheres via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm). The presence of poly(NIPAAm) (PNIPAAm) brushes on the obtained MIP microspheres was confirmed by FT-IR as well as the water dispersion and static contact angle experiments, and some quantitative information including the molecular weights and polydispersities of the grafted polymer brushes, the thickness of the polymer brush layers, and their grafting densities was provided. In addition, the binding properties of the ungrafted and grafted MIPs/NIPs in both methanol/water (4/1, v/v) and pure water solutions were also investigated. The introduction of PNIPAAm brushes onto the MIP microspheres has proven to significantly improve their surface hydrophilicity and impart stimuli-responsive properties to them, leading to their pure water-compatible and thermo-responsive binding properties. The application of the facile surface-grafting approach, together with the versatility of RAFT polymerization and the availability of many different functional monomers, makes the present methodology a general and promising way to prepare water-compatible and stimuli-responsive MIPs for a wide range of templates. PMID:20837394

Pan, Guoqing; Zhang, Ying; Guo, Xianzhi; Li, Chenxi; Zhang, Huiqi

2010-11-15

172

The influence of crosslinker on the properties of radiation-grafted films and membranes based on ETFE  

Microsoft Academic Search

Crosslinked proton-exchange membranes were prepared by radiation-induced grafting of styrene into poly(ethylene-alt-tetrafluoroethylene) (ETFE) and subsequent sulfonation. The influence of the crosslinker, divinylbenzene (DVB), on various film and membrane properties was investigated in detail. A series of grafted films and membranes were prepared at varying DVB concentrations at a fixed graft level (?25%) for this purpose. Grafting kinetics and kinetic parameters,

Hicham Ben youcef; Selmiye Alkan Gürsel; Alexander Wokaun; Günther G. Scherer

2008-01-01

173

Primary processes of the radiation-induced cationic polymerization of ?-methylstyrene enhanced by triphenylsulfonium hexafluorophosphate  

NASA Astrophysics Data System (ADS)

Primary processes of the radiation-induced cationic polymerization of ?-methylstyrene in dichloromethane solution containing (C 6H 5) 3SPF 6, which enhances the polymerization, were studied by pulse radiolysis. The yield and lifetime of ?-methylstyrene dimer radical cations are increased by the addition of the salt. This has been attributed to the stabilization of the monomer and dimer radical cations toward neutralization through ion-pair formation with PF 6-. The effect of ( n-C 4H 9) 4NPF 6 observed by the pulse radiolysis is similar to that of (C 6H 5) 3SPF 6, but the former salt does not enhance the polymerization probably because of a radiolysis product, tributylamine, inhibiting the polymerization. Comparison is made with the previous results for (C 6H 5) 2IPF 6 which also enhances the polymerization.

Mah, Soukil; Yamamoto, Yukio; Hayashi, Koichiro

174

Application of Sepharose and Sephadex modified by means of radiation grafting in separation of biomolecules  

NASA Astrophysics Data System (ADS)

In this work Sepharose-NASI-BSA and Sephadex-NASI-BSA were prepared by means of pre-irradiation grafting and direct radiation grafting separately. The radiation grafting condition were given. In order to get those compounds the conjugation reaction between NASI and BSA was investigated as well. The reaction was performed at 37 °C for 2hs, but in the case of Sephadex-NASI, it took longer time, 6hs, to finish the conjugation reaction. The application of the radiation modified matrixes as a kind of filling materials of column chromatography in separation of D,L-tryptophans was studied. The results showed that this method was accessible after some improvements.

Li, Jun; Yi, Min; Ha, Hongfei

1995-02-01

175

Radiation-induced polymerization of acrylamide within Okoume ( Aucoumea klaineana pierre)  

Microsoft Academic Search

Polymerization of acrylamide absorbed in Okoume (Aucoumea klaineana pierre), was induced by gamma-ray irradiation. Polymer loading and tensile strength of the resulting wood polymer composites were studied. The role of radiation dose and the effect of the additives, sulfuric acid (H+), N-vinyl pyrrolidone, trimethylolpropane triacrylate and urea, and co-additives on monomer system polymerization were also investigated. Methanol, water and water\\/methanol

Elias Hanna Bakraji; Numan Salman; Ibrahim Othman

2002-01-01

176

Radiation and UV Grafting of Monomers to Polyolefins and Cellulose Acetate. Significance of These Studies in Reagent Insolubilization Reactions  

Microsoft Academic Search

In the simultaneous irradiation procedure, sensitized W radiation is shown to be a complementary initiator to ionizing radiation for the grafting of monomers to polyolefins. Parameters influencing the yield of graft have been considered, including the role of sensitizer, solvent, and the type of monomer. These results indicate why difficulties have been experienced by previous authors in photografting monomers to

Chye H. Ang; John L. Garnett; Ronald Levot; Mervyn A. Long; Kenneth J. Nicol

1982-01-01

177

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization  

PubMed Central

Summary The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP.

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann

2013-01-01

178

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization.  

PubMed

The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a "grafting from" process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP. PMID:23946859

Moreira, Guillaume; Charles, Laurence; Major, Mohamed; Vacandio, Florence; Guillaneuf, Yohann; Lefay, Catherine; Gigmes, Didier

2013-01-01

179

Protective immunity to UV radiation-induced skin tumours induced by skin grafts and epidermal cells  

Microsoft Academic Search

There is little evidence that cutaneous dendritic cells (DC), including epidermal Langerhans cells (LC), can induce immunity to UV radiation (UVR)-induced skin tumours. Here, it is shown that cells within skin can induce protective antitumour immunity against a UVR-induced fibrosarcoma. Transplantation of the skin overlying subcutaneous tumours onto naïve recipients could induce protective antitumour immunity, probably because the grafting stimulated

Ronald Sluyter; Kylie S Yuen; Gary M Halliday

2001-01-01

180

Role of additives in wood polymer composites. Relationship to analogous radiation grafting and curing processes  

NASA Astrophysics Data System (ADS)

Wood polymer composites (WPC) were prepared by impregnating an Australian softwood, Pinus radiata with methyl methacrylate which subsequently underwent in situ polymerisation utilising either ? radiation or the catalyst-accelerator method. Novel additives including thermal initiator, crosslinking agents, an inclusion compound and oxygen scavenger were incorporated to improve the polymer loading and properties of the resulting WPC. Polymer loadings of WPC obtained utilising the accelerator-catalyst method corresponded well with those obtained using ? radiation with 20 kGy radiation dose. The mechanistic significance of the current work in analogous radiation grafting and curing processes is discussed.

Ng, Loo-Teck; Garnett, John L.; Mohajerani, Shahroo

1999-08-01

181

Radiation-induced polymerization of acrylamide within Okoume ( Aucoumea klaineana pierre)  

NASA Astrophysics Data System (ADS)

Polymerization of acrylamide absorbed in Okoume ( Aucoumea klaineana pierre), was induced by gamma-ray irradiation. Polymer loading and tensile strength of the resulting wood polymer composites were studied. The role of radiation dose and the effect of the additives, sulfuric acid (H +), N-vinyl pyrrolidone, trimethylolpropane triacrylate and urea, and co-additives on monomer system polymerization were also investigated. Methanol, water and water/methanol mixtures were used as the swelling agents. In general, the use of additives and co-additives brought about an enhancement of tensile strength and polymer loading of the composites. In some cases, additives also lowered the monomer concentration and the gamma-radiation dose required for polymerization.

Bakraji, Elias Hanna; Salman, Numan; Othman, Ibrahim

2002-07-01

182

Synergistic Effect on Corrosion Resistance of Phynox Substrates Grafted with Surface-Initiated ATRP (Co)polymerization of 2-Methacryloyloxyethyl Phosphorylcholine (MPC) and 2-Hydroxyethyl Methacrylate (HEMA).  

PubMed

Phynox is of high interest for biomedical applications due to its biocompatibility and corrosion resistance. However, some Phynox applications require specific surface properties. These can be imparted with suitable surface functionalizations of its oxide layer. The present work investigates the surface-initiated atom transfer radical polymerization (ATRP) of 2-methacryloyoxyethyl phosphorylcholine (MPC), 2-hydroxyethyl methacrylate (HEMA), and ATRP copolymerization of (HEMA-co-MPC) (block and statistic copolymerization with different molar ratios) on grafted Phynox substrates modified with 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) as initiator. It is found that ATRP (co)polymerization of these monomers is feasible and forms hydrophilic layers, while improving the corrosion resistance of the system. PMID:24915233

Barthélémy, Bastien; Maheux, Simon; Devillers, Sébastien; Kanoufi, Frédéric; Combellas, Catherine; Delhalle, Joseph; Mekhalif, Zineb

2014-07-01

183

Influence of Space Radiation on the Outgassing Rate of a Patterned Polymeric Composite in Vacuum  

SciTech Connect

Experimental results on outgassing rates of patterned polymeric composites preliminary subjected to separate and combined radiation have been analyzed and presented. Mathematical models describing the outgassing processes in these materials were used for interpretation of the experimental data. Numerical results found using the models are presented.

Khasanshin, R. H.; Timofeev, A. N. [Joint-stock company 'Kompozit' 4, Pionerskay str., 141070 Korolev, Moscow region, Russia, tel. 513-20-20 (Russian Federation); Ivanov, M. F. [Joint Institute for High Temperatures of Russian Academy of Sciences Moscow (Russian Federation)

2009-01-05

184

Study on slow release anti-cancer drugs prepared by radiation induced polymerization  

Microsoft Academic Search

This paper reports the research results which the anticancer drugs Ara-C with controlled slow release were made by radiation induced polymerization of monomers such as methacrylates at room temperature. Our studies showed that not only hydrophilic synthetic polymers but also hydrophobic polymers such as hydrophobic methacrylates (including MMA, EMA, and BMA) could be used to the immobilization. In vitro the

Xie Huaijiang; Song Juzhong; Peng Tao

1993-01-01

185

Real time in situ spectroscopic characterization of radiation induced cationic polymerization of glycidyl ethers  

NASA Astrophysics Data System (ADS)

Radiation curable polymeric materials suffer from relatively poor mechanical properties. Moreover, the curing behavior of such systems (i.e. the exact relationship between chemical kinetics and key processing variables) is not fully understood. In order to design improved epoxy based electron beam (EB) curable systems, and in order to develop appropriate process models, a detailed knowledge of the kinetics of epoxy cationic polymerization induced by ultraviolet (UV) or EB irradiation is required. In this work, we present our development of a technique based on real time near infrared (RTIR) spectroscopy for performing in situ kinetic analysis of radiation induced cationic polymerization of epoxy systems. To our knowledge this is the first time such data have been collected and presented for high-energy EB (10 MeV) induced polymerization. A demonstration of the technique for deterministic evaluation of degree of cure is shown using model glycidyl ether (phenyl glycidyl ether and diglycidyl ether of bisphenol A) resins and isothermal curing conditions. The impact of initiation rate on polymerizations with UV and EB for the cationic initiator is directly evident by comparative analysis. The sensitivity of the RTIR method and ability to produce quantitative data evidence of reaction mechanisms is demonstrated. The type of data presented in this work forms the basis for cure models being developed.

Mascioni, Matteo; Sands, James M.; Palmese, Giuseppe R.

2003-08-01

186

New polymeric gel electrolytes consisting of oligo(ethylene oxide)-grafted polymethacrylate matrices for rechargeable lithium batteries  

Microsoft Academic Search

Lithium ion conductors with novel polymeric matrices have been developed for rechargeable lithium batteries operating at ambient temperature. The polymeric electrolytes were prepared by photo-induced radical co-polymerization of mixtures of ethylmethacryl-methyl carbonate (EMMC) and diethyleneglycol dimethacrylate (DEGDM) dissolving LiClO4 with propylene carbonate (PC) as plasticizing solvent. The resulting composite films were homogeneous, flexible and self-standing. The ionic conductivity depended much

Masayuki Morita; Masashi Ishikawa; Katsushi Asanomi

1998-01-01

187

Radiation induced polymerization of vinyl monomers and their application for preparation of wood-polymer composites  

NASA Astrophysics Data System (ADS)

Polymerizing effects of high energy radiation has been found suitable for preparation of wood-polymer composites. In the present work after evaluating polymer products that have been obtained by irradiation method, wood-polymer composites have been prepared by in situ polymerization of vinyl acetate, acrylic acid and acrylic acid/styrene mixture using two samples of Iranian hardwoods, Beech and Hornbeam. These woods and their composites have been tested for their physical and mechanical properties. The results have shown that chemical bonding between polymer and the cell wall component lead to better strength properties in the composites.

Sheikh, N.; Afshar Taromi, F.

1993-07-01

188

The role of partitioning of reagents in grafting and curing reactions initiated by ionizing radiation and UV  

Microsoft Academic Search

Experimental evidence involving monomer absorption studies using tritiated styrene is shown to support the proposal that additives such as mineral acids and certain inorganic salts when dissolved in the monomer solution enhance radiation grafting yields by a mechanism involving partitioning of reagents. Photoinitiators such as benzoin ethyl ether and its methyl analogue are reported as new additives for grafting of

R. P. Chaplin; P. A. Dworjanyn; N. J. W. Gamage; J. L. Garnett; S. V. Jankiewicz; M. A. Khan; D. F. Sangster

1996-01-01

189

Novel ETFE based radiation grafted poly(styrene sulfonic acid- co-methacrylonitrile) proton conducting membranes with increased stability  

Microsoft Academic Search

Styrene radiation grafted ETFE based proton conducting membranes are subject to degradation under fuel cell operating conditions and show a poor stability. Lifetimes exceeding 250h can only be achieved with crosslinked membranes. In this study, a novel approach based on the increase of the intrinsic oxidative stability of uncrosslinked membranes is reported. Hence, the co-grafting of styrene with methacrylonitrile (MAN),

Hicham Ben youcef; Lorenz Gubler; Selmiye Alkan Gürsel; Dirk Henkensmeier; Alexander Wokaun; Günther G. Scherer

2009-01-01

190

Surface modification of nanofiltration membranes to improve the removal of organic micro-pollutants (EDCs and PhACs) in drinking water treatment: Graft polymerization and cross-linking followed by functional group substitution  

Microsoft Academic Search

A commercially available thin film composite (TFC) polyamide (PA) nanofiltration (NF) membrane was chemically modified to improve its rejection capacity for selected organic micro-pollutants categorized as endocrine disrupting chemicals (EDCs) and pharmaceutically active compounds (PhACs): bisphenol-A (BPA), ibuprofen, and salicylic acid. The raw NF membrane was altered using the following modification sequence: graft polymerization (methacrylic acid (MA)-membrane); cross-linking of grafted

Jae-Hyuk Kim; Pyung-Kyu Park; Chung-Hak Lee; Heock-Hoi Kwon

2008-01-01

191

Self-assembly and graft polymerization route to Monodispersed Fe3O4@SiO2--polyaniline core-shell composite nanoparticles: physical properties.  

PubMed

This study describes the synthesis of monodispersed core-shell composites of silica-modified magnetic nanoparticles and conducting polyaniline by self-assembly and graft polymerization. Magnetic ferrite nanoparticles (Fe3O4) were prepared by coprecipitation of Fe+2 and Fe+3 ions in alkaline solution, and then silananized. The silanation of magnetic particles (Fe3O4@SiO2) was carried out using 3-bromopropyltrichlorosilane (BPTS) as the coupling agent. FT-IR spectra indicated the presence of Fe--O--Si chemical bonds in Fe3O4@SiO2. Core-shell type nanocomposites (Fe3O4@SiO2/PANI) were prepared by grafting polyaniline (PANI) on the surface of silanized magnetic particles through surface initiated in-situ chemical oxidative graft polymerization. The nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared (FTIR) spectra, UV-visible spectroscopy, photoluminescence (PL) spectra, electrical conductivity and magnetic characteristics. HRTEM images of the nanocomposites revealed that the silica-modified magnetic particles made up the core while PANI made up the shell. The XPS spectrum revealed the presence of silica in the composites, and the XRD results showed that the composites were more crystalline than pure PANI. PL spectra show that composites exhibit photoluminescent property. Conductivity of the composites (6.2 to 9.4 x 10(-2) S/cm) was higher than that of pristine PANI (3.7 x 10(-3) S/cm). The nanocomposites exhibited superparamagnetism. Formation mechanism of the core-shell structured nanocomposites and the effect of modified magnetic nanoparticles on the electro-magnetic properties of the Fe3O4@SiO2/PANI nanocomposites are also investigated. This method provides a new strategy for the generation of multi-functional nanocomposites that composed of other conducting polymers and metal nanoparticles. PMID:19198281

Reddy, Kakarla Raghava; Lee, Kwang-Pill; Kim, Ju Young; Lee, Youngil

2008-11-01

192

Swelling characteristics of konjac glucomannan superabsobent synthesized by radiation-induced graft copolymerization  

NASA Astrophysics Data System (ADS)

Graft copolymerization of konjac glucomannan (KGM) and acrylic acid was induced by 60Co-? irradiation at room temperature. The effects of radiation dose and monomer-to-KGM ratio on grafting yield and equilibrium water absorbency were investigated. The KGM-based superabsorbent polymer (KSAP) could absorb water 625 times of its dry weight when the radiation dose was 5.0 kGy and monomer-to-KGM ratio was 5. The structure of KSAP was characterized by FTIR, XRD, and SEM. KSAP showed a lower crystallinity than KGM. The porous microstructure of KSAP was revealed by SEM. The diffusion mechanism of water in the hydrogel is consistent with the anomalous diffusion model. Cations, especially multivalent cations, greatly reduced water absorbency of KSAP. Rising temperature, acidic or basic solutions are not favorable for the swelling of KSAP.

Wu, Jia; Deng, Xiao; Lin, Xiangyang

2013-02-01

193

Synthesis and Electrical Properties of Polyaniline/Polyaniline Grafted Multiwalled Carbon Nanotube Mixture via In Situ Static Interfacial Polymerization.  

National Technical Information Service (NTIS)

The mixture of polyaniline (PANi) and PANi grafted multiwalled carbon nanotube (PANi-g-MWNT) was prepared by a two-step reaction sequence. MWNT was first functionalized with 4-aminobenzoic acid via 'direct' Firedel- Crafts acylation in polyphosphoric acid...

I. Jeon J. Baek L. Tan

2010-01-01

194

A rare example of the formation of polystyrene-grafted aliphatic polyester in one-pot by radical polymerization.  

PubMed

The radical copolymerization of cyclic ester ?-propiolactone (?-PL) with styrene (St) at 120?°C, with a complete range of monomer ratios, is a rare example of a system providing graft copolymers (PSt-g-?-PL) in one pot. The structure of the resulting ?-PL-St copolymers was proven by using a combination of different characterization techniques, such as 1D and 2D NMR spectroscopy and gel permeation chromatography (GPC), before and after alkaline hydrolysis of the polymers. The number of grafting points increased with an increasing amount of ?-PL in the feed. A significant difference in the reactivity of St and ?-PL and radical chain-transfer reactions at the polystyrene (PSt) backbone, followed by combination with the active growing poly(?-PL) chains, led to the formation of graft copolymers by a grafting-onto mechanism. PMID:24806996

Shi, Yinfeng; Zheng, Zhicheng; Agarwal, Seema

2014-06-10

195

Preparation and characterization of a magneto-polymeric nanocomposite: Fe 3O 4 nanoparticles in a grafted, cross-linked and plasticized poly(vinyl chloride) matrix  

NASA Astrophysics Data System (ADS)

In this work two kind of materials: (1) grafted, cross-linked and plasticized poly(vinyl chloride) (PVC) "plastic films" and (2) magnetic plastic films "magneto-polymeric nanocomposites" were prepared. Precursor solutions or "plastisols" used to obtain the plastic films were obtained by mixing PVC (emulsion grade) as polymeric matrix, di(2-ethylhexyl)phthalate (DOP) as plasticizer, a thermal stabilizer based in Ca/Zn salts, and a cross-linking agent, 3-mercaptopropyltrimethoxysilane (MTMS) or 3-aminopropyltriethoxysilane (ATES), at several concentrations. Flexible films were obtained from the plastisols using static casting. The stress-strain behavior and the gel content (determined by Soxhlet extraction with boiling THF) of the flexible films were measured in order to evaluate the effect of the cross-linking agent and their content on the degree of cross-linking. The magneto-polymeric nanocomposites were obtained by mixing the optimum composition of the plastisols (analyzed previously) with magnetite (Fe 3O 4)-based ferrofluid and DOP. Later, flexible films were obtained by static casting of the plastisol/ferrofluid systems. The magnetic films were characterized by the above-mentioned techniques and X-ray diffraction, vibrating sample magnetometry and thermogravimetrical analysis.

Rodríguez-Fernández, Oliverio S.; Rodríguez-Calzadíaz, C. A.; Yáñez-Flores, Isaura G.; Montemayor, Sagrario M.

196

Self-assembled heterostructures based on triethylenetetraamine grafted ppv, polymeric dyes and complexed metals ions: Structure and energy transfer  

Microsoft Academic Search

Poly(phenylenevinylene) (PPV) grafted with triethylenetetramine (TETA), PPV:TETA, unlike PPV, can interact with anionic sulfonated polymer dyes and can also coordinate metal ions, `eg Eu, by chelation with the grafted TETA moiety. We have used these interactions and chelation to construct two types of self-assembled films using the layer-by-layer self-assembly technique. Structural characterization by means of specular X-ray reflectivity of heterostructures

H. Hong; I. Benjamin; S. Kirstein; Y. Avny; R. Neumann; D. Davidov

1999-01-01

197

Synthesis and characterization of thermo- and pH- sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

NASA Astrophysics Data System (ADS)

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that the grafting percentage and grafting efficiency increased with the increase of monomer concentration and total irradiation dose. The highest grafting percentage is 620%, the lower critical solution temperature (LCST) of this hydrogel is about 28 °C.

Cai, Hong; Zhang, Zheng Pu; Chuan Sun, Ping; Lin He, Bing; Xia Zhu, Xiao

2005-09-01

198

Chemical and radiation crosslinked polymer electrolyte membranes prepared from radiation-grafted ETFE films for DMFC applications  

Microsoft Academic Search

To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), doubly crosslinked membranes were prepared by chemical crosslinking using bifunctional monomers, such as divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE), and by radiation crosslinking. The membranes were prepared by grafting of m,p-methylstyrene (MeSt) and p-tert-butylstyrene (tBuSt) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent

Jinhua Chen; Masaharu Asano; Tetsuya Yamaki; Masaru Yoshida

2006-01-01

199

Polymer-grafted multi-walled carbon nanotubes through surface-initiated ring-opening polymerization and click reaction  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWNTs) are modified to possess the hydroxyl groups and are used as coinitiators to polymerize poly(?-caprolactone) (PCL) or poly(?-chloro-?-caprolactone) (P?ClCL) by surface-initiated ring-opening polymerization. Pendent chlorides were converted into azides by the reaction with sodium azides. Finally, various types of terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen’s 1,3-dipolar cycloaddition (click reaction). Chemical structure of

Ren-Shen Lee; Wen-Hsin Chen; Jarrn-Horng Lin

2011-01-01

200

Fabrication of PEFC membrane based on PTFE/FEP polymer-alloy using radiation-grafting  

NASA Astrophysics Data System (ADS)

Polymer electrolyte fuel cells (PEFC) membranes based on very thin film of network polytetrafluoroethylene (PTFE)/tetrafluoroethylene-co-hexafluoropropylene (FEP) polymer-alloy (PTFE/FEP polymer-alloy: FE), have been fabricated by radiation-grafting with reactive styrene monomers using electron beam irradiation (EB) under nitrogen atmosphere at room temperature. The characteristic properties of obtained materials have been measured by ion exchange capacity (IEC), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and so on. The grafting yields showed the initial rapid increase, and then tended to saturate above 5-8 h. The grafting yields of all FE with various network densities have been achieved 80-100%. The styrene-grafted materials were sulfonated by chlorosulfonic acid. The IECs of sulfonated materials based on FE polymer-alloy have been achieved 3.0 meq/g. This suggests that IEC value is independent on network density and PTFE/FEP blend ratio. The IEC values of obtained materials are about three times higher than those of commercial perfluoro-sulfonic acid (PFSA) membranes. By small angle X-ray scattering (SAXS), it is found that the higher network densities would give the smaller cluster sizes in sulfonated materials. Thus, the higher amount of FEP will give the smaller cluster formation of sulfonated materials.

Asano, Saneto; Mutou, Fumihiro; Ichizuri, Shogo; Li, Jingye; Miura, Takaharu; Oshima, Akihiro; Katsumura, Yosuke; Washio, Masakazu

2005-07-01

201

A novel preparation of surface-modified paramagnetic magnetite\\/polystyrene nanocomposite microspheres by radiation-induced miniemulsion polymerization  

Microsoft Academic Search

A novel and facile approach to the preparation of paramagnetic magnetite\\/polystyrene nanocomposite microspheres by 60Co ?-ray radiation-induced miniemulsion polymerization is reported. First, we modified the magnetite nanoparticles (MPs) with a Y-shaped surfactant: 12-hexanoyloxy-9-octadecenoic acid (HOA). Nanocomposite microspheres consisting of polystyrene–iron oxide nanoparticles then were prepared by the radiation-induced miniemulsion polymerization of styrene in the presence of HOA-modified MPs using HOA

Zhen Qian; Zhicheng Zhang; Yun Chen

2008-01-01

202

Fundamental investigation of ultraviolet radiation effects in polymeric film-forming materials  

NASA Technical Reports Server (NTRS)

A literature search from 1958 to present was conducted on the effect of ultraviolet radiation on polymeric materials, with particular emphasis on vacuum photolysis, mechanisms of degradation, and energy transfer phenomena. The literature from 1958 to 1968 was searched manually, while the literature from 1968 to present was searched by using a computerized keyword system. The primary objective was to provide the necessary background information for the design of new or modified materials with improved stability to the vacuum-radiation environment of space.

Giori, C.; Yamauchi, T.; Llewellen, P.; Gilligan, J.

1974-01-01

203

In-situ radiation dosimetry based on radio-fluorogenic co-polymerization  

NASA Astrophysics Data System (ADS)

A fluorimetric method of radiation dosimetry is presented for which the intensity of the fluorescence of a (tissue equivalent) medium is linearly dependent on accumulated dose from a few Gray up to kiloGrays. The method is based on radio-fluorogenic co-polymerization (RFCP) in which a normally very weakly fluorescent molecule becomes highly fluorescent when incorporated into a (radiation-initiated) growing polymer chain. The method is illustrated with results of in-situ measurements within the chamber of a cobalt-60 irradiator. It is proposed that RFCP could form the basis for fluorimetric multi-dimensional dose imaging.

Warman, John M.; Luthjens, Leonard H.; de Haas, Matthijs P.

2009-05-01

204

Preparation of poly(vinyltetrazole) chain-grafted poly(glycidymethacrylate-co-ethylenedimethacrylate) beads by surface-initiated atom transfer radical polymerization for the use in weak cation exchange and hydrophilic interaction chromatography.  

PubMed

A novel stationary phase for weak cation exchange (WCX) and hydrophilic interaction chromatography (HILIC) was prepared with surface-initiated atom transfer radical polymerization (SI-ATRP). Vinyltetrazole was grafted onto the surface of the beads in water medium with the polyglycidylmethacrylate beads (P(GMA/EDMA)) previously modified with 2-bromoisobutryl bromide as the macromolecule initiators and CuCl as catalyst. The poly(vinyltetrazole)-grafted beads obtained with different atom transfer radical polymerization (ATRP) formulations were tried as chromatographic packings in ion-exchange chromatography. The results showed that the prepared columns could separate the tested proteins with high efficiency and high capacity, and the retention time of protein had a positive relationship with increasing the chain lengths of the grafted poly(vinyltetrazole) (PVT). The prepared column was also found to be able to separate nucleosides by hydrophilic interaction chromatographic mode. PMID:21645729

Hao, Junxia; Wang, Fuqiang; Dai, Xiaojun; Gong, Bolin; Wei, Yinmao

2011-07-15

205

Grafting of methyl methacrylate to cellulose and polypropylene with UV and ionising radiation in the presence of additives including CT complexes  

NASA Astrophysics Data System (ADS)

Detailed studies of the grafting of polar methyl methacrylate (MMA) to two representative backbone polymers, cellulose and polypropylene (PPE) in the presence of additives, using ionising radiation and UV as initiating sources, are reported. The results are compared with analogous grafting work with non polar styrene previously studied. The additives chosen for examination were predominantly components used in radiation curing formulations since grafting and curing are known to be mechanistically related. The additives were mineral acid, photoinitiators, vinyl ethers, oligomers, polyfunctional monomers including multifunctional acrylates (MFAs) and methacrylates (MFMAs). For the first time charge transfer (CT) monomer complexes have been used as additives in the current work. The CT complexes themselves, being monomers, have also been directly radiation grafted to cellulose. Mechanisms for the above grafting processes are proposed. The significance of this grafting work in analogous radiation curing is discussed. The grafting of the CT complexes, themselves, is shown to lead to new copolymers with potential industrial applications.

Garnett, John L.; Ng, Loo-Teck; Viengkhou, Visay

1999-10-01

206

Radiation-induced grafting of carbon nanotubes on HPLC silica microspheres: theoretical and practical aspects.  

PubMed

Multi-walled carbon nanotubes (MWCNTs) were grafted for the first time by ?-radiation onto silica microspheres in the presence of polybutadiene (PB) as the linking agent, obtaining a novel hybrid material with chromatographic properties, with an alternative approach to the existing procedures. The synthesis involves the one-pot ?-radiation-induced grafting of MWCNTs onto silica microspheres in the presence of PB as a linking agent. PB also serves as a coating layer of the silica particles, to which MWCNTs are anchored through stable chemical bonds formed via radical chain reaction with the polymer. The product (MWCNT-PB-modified silica) resulted in MWCNT bundles interlaying the silica particles which acted as a support and as a spacer. This new material highlights the unquestionable properties of CNTs also when grafted in a composite, thus allowing the disposition of a more robust material whose properties are still related to the nanotube structure. The grafting was confirmed by Raman spectroscopy. The surface area, determined by BET isotherms, resulted in 132 m(2) g(-1), about 34% lower than that of pure silica, pointing to the cross-linking effect of PB in the silica matrix. The evaluation of MWCNT-PB-modified silica as a LC stationary phase was performed by separation of aromatics, with satisfactory resolution and reproducibility, while structural selectivity was proved by isomer separation. A good resolution was obtained also for acid/basic compounds as barbiturates. A comparison with a commercial C18 sorbent highlighted the advantage in using the CNT column for separating aromatic hydrocarbons. Control experiments on the PB-coated silica column proved the key role of MWCNTs in the chromatographic performance. PMID:23678482

Speltini, Andrea; Merli, Daniele; Dondi, Daniele; Milanese, Chiara; Galinetto, Pietro; Bozzetti, Carlo; Profumo, Antonella

2013-07-01

207

Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry  

NASA Astrophysics Data System (ADS)

A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu3+) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu3+ ions afforded photoluminescent Eu3+ tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu3+). The structure, morphology, and fluorescence properties of the Eu3+ coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu3+ nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu3+ nanohybrid complexes were investigated by photoluminescence spectroscopy.

Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek

2013-07-01

208

Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)  

PubMed Central

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

2008-01-01

209

Synthesis and characterization of ?-CD-coated polystyrene microspheres by ?-ray radiation emulsion polymerization.  

PubMed

Polystyrene (PS) microspheres coated with ?-cyclodextrin (?-CD) were fabricated via ?-ray-induced emulsion polymerization in a ternary system of styrene/?-CD/water (St/?-CD/water). The solid inclusion complex of St and ?-CD particles formed at the St droplets-water interface can stabilize the emulsion as the surfactant. TEM and XPS results showed that ?-CD remains on the surface of PS particles. The average size of the PS particles increases from 186 to 294 nm as the weight ratio of ?-CD to St rises from 5% to 12.5%. The water contact angle (CA) of PS latex film is lower than 90°, and reduces with the ?-CD content even to 36°. Thus, this work provides a new and one-pot strategy to surface hydrophilic modification on hydrophobic polymer particles with cyclodextrins through radiation emulsion polymerization. PMID:22887797

Xu, Dezhi; Wang, Mozhen; Ge, Xuewu; Lam, Michael Hon-Wah

2012-11-23

210

Radiation-induced grafting of inorganic particles onto polymer backbone: A new method to design polymer-based nanocomposite  

NASA Astrophysics Data System (ADS)

Polypropylene/polyhedral oligomeric silsesquioxane (PP/POSS) nanocomposites were prepared by in situ radiation-induced grafting of POSS onto PP. Radiation-induced grafting of POSS was confirmed by FT-IR spectroscopy. The mechanical property of PP/POSS nanocomposites increased with the increase in POSS content and with the increase in absorption dose up to 5 kGy, above which it started to decrease. The reduction of mechanical property at high doses can be attributed to the chain scission of PP by radiation. The degree of reduction in decomposition temperature of irradiated PP/POSS nanocomposites was found to be much less than that of neat PP due to the covalent grafting of POSS onto PP by radiation.

Choi, Jae-Hak; Jung, Chan-Hee; Kim, Dong-Ki; Ganesan, Ramakrishnan

2008-01-01

211

Radiation-induced graft copolymerization of styrene with vinylic monomers at high dose rates  

NASA Astrophysics Data System (ADS)

Radiation-induced graft copolymerization of the following monomer pairs: styrene-acrylonitrile (AN), styrene-methyl methacrylate (MMA), styrene-2-methyl-5-vinylpyridine (MVP) and styrene- acrylic acid (AA) onto polyethylene film was studied at room temperature in the range of dose rates 8.10 -2-6.10 3 Gy/s. The grafted copolymer compositions were determined and copolymerization reactivity ratios were calculated. At high dose rates the contribution of the ionic mechanism is proved by the change of the copolymer compositions obtained at essential different dose rates and by different influence of the donor and acceptor solvents on this process. It is established that transition from radical mechanism to ionic one begins in the interval of dose rates 10 2-10 3 Gy/s for styrene-AN, styrene-MMA, styrene-MVP systems but occurs in the interval of dose rates 10 3-6.10 3 Gy/s for styrene-AA system. The formation of the grafted polymer compositions, obtained at high dose rates, must be described by the kinetics which takes into account the presence of ionic process.

Kabanov, V. Ya.; Aliev, R. E.

212

Synthesis and characterization of thermo- and pH sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via ?-radiation  

Microsoft Academic Search

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via ?-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP\\/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that

Hong Cai; Zheng Pu Zhang; Ping Chuan Sun; Bing Lin He; Xiao Xia Zhu

2005-01-01

213

Synthesis and characterization of thermo- and pH sensitive hydrogels based on Chitosan-grafted N-isopropylacrylamide via gamma-radiation  

Microsoft Academic Search

Thermo- and pH-sensitive hydrogels were prepared by graft copolymerization of chitosan (CS) and N-isopropylacrylamide via gamma-radiation. The effects of monomer concentration and irradiation dose on grafting percentage and grafting efficiency were studied. The graft copolymers were characterized by 13C CP\\/MAS NMR and thermogravimetric analysis. The pH and thermosensitivity and swelling properties of the hydrogels were investigated. The results showed that

Hong Cai; Zheng Pu Zhang; Ping Chuan Sun; Bing Lin He; Xiao Xia Zhu

2005-01-01

214

Radiation Protection Effectiveness of Polymeric Based Shielding Materials at Low Earth Orbit  

NASA Technical Reports Server (NTRS)

Correlations of limited ionizing radiation measurements onboard the Space Transportation System (STS; shuttle) and the International Space Station (ISS) with numerical simulations of charged particle transport through spacecraft structure have indicated that usage of hydrogen rich polymeric materials improves the radiation shielding performance of space structures as compared to the traditionally used aluminum alloys. We discuss herein the radiation shielding correlations between measurements on board STS-81 (Atlantis, 1997) using four polyethylene (PE) spheres of varying radii, and STS-89 (Endeavour, 1998) using aluminum alloy spheres; with numerical simulations of charged particle transport using the Langley Research Center (LaRC)-developed High charge (Z) and Energy TRaNsport (HZETRN) algorithm. In the simulations, the Galactic Cosmic Ray (GCR) component of the ionizing radiation environment at Low Earth Orbit (LEO) covering ions in the 1< or equals Z< or equals 28 range is represented by O'Neill's (2004) model. To compute the transmission coefficient for GCR ions at LEO, O'Neill's model is coupled with the angular dependent LaRC cutoff model. The trapped protons/electrons component of LEO environment is represented by a LaRC-developed time dependent procedure which couples the AP8min/AP8max, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment resulting from interaction of GCR ions with upper atmosphere is modeled through extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. With the validity of numerical simulations through correlation with PE and aluminum spheres measurements established, we further present results from the expansion of the simulations through the selection of high hydrogen content commercially available polymeric constituents such as PE foam core and Spectra fiber(Registered TradeMark) composite face sheet to assess their radiation shield properties as compared to generic PE.

Badavi, Francis F.; Stewart-Sloan, Charlotte R.; Wilson, John W.; Adams, Daniel O.

2008-01-01

215

Radiation-grafting of 2-hydroxyethylmethacrylate and oligo (ethylene glycol) methyl ether methacrylate onto polypropylene films by one step method  

NASA Astrophysics Data System (ADS)

Polypropylene films were modified with 2-hydroxyethylmethacrylate (HEMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA) using the pre-irradiation method with gamma-rays (one step method). The effect of absorbed dose from 10 to 100 kGy, temperature (50, 60, and 70 °C), monomer concentration between 12.5% and 62.5%, monomers ratio from 10% to 90% and reaction time from 5 to 50 h; on the degree of grafting was determined. The grafted samples were analyzed by FTIR-ATR, TGA, DSC, swelling, and contact angle. Grafts onto polymeric films between 3% and 109% were obtained at doses from 10 to 100 kGy and a dose rate around 7.4 kGy/h. The graft percent increased with the content in HEMA in the HEMA:OEGMA feed mixture, which indicates a lower reactivity of OEGMA compared to HEMA. The hydrogel layer grafted on the polypropylene substrate increases the hydrophilicity of the surface and also provides certain temperature-responsiveness, which may be of interest for biomedical applications.

Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2012-01-01

216

Grafting of thermoresponsive polymer from the surface of functionalized multiwalled carbon nanotubes via atom transfer radical polymerization  

Microsoft Academic Search

Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and H2SO4 to introduce carboxylic groups onto carbon nanotubes surfaces. The oxidized carbon nanotubes were reacted subsequently with\\u000a thionyl chloride and 2-Hydroxylethyl-2?-bromoisobutyrate, producing MWNT-based macroinitiators, MWNT-Br, for the atom transfer\\u000a radical polymerization of (N-isopropylacrylamide). FTIR, XPS, 1H NMR, Raman and TGA were used to characterize the resulting products and to determine the

GuoYong Xu; Ru Xia; Hu Wang; XiangChun Meng; QingRen Zhu

2008-01-01

217

Semi-interpenetrating polymer networks of poly(3-hydroxybutyrate) prepared by radiation-induced polymerization  

NASA Astrophysics Data System (ADS)

Semi-interpenetrating polymer networks (IPNs) based on bacterial poly(3-hydroxy butyrate) with a hydrophilic monomer at different compositions were prepared by radiation-induced polymerization using ?-rays from a 60Co source with a total dose of 10-100 kGy. The swelling behaviour was determined by water content at equilibrium, while thermal properties and crystallinity were studied by differential scanning calorimetry. Extraction of the soluble part of PHB from the films at low and high temperature with water or chloroform as well as FTIR data indicate the occurrence of the crosslinking reaction in the hydrogels. The results show a water uptake increasing with the hydrophilic component until 25%.

Martellini, Flavia; Innocentini Mei, Lúcia H.; Lora, Silvano; Carenza, Mario

2004-09-01

218

Synthesis of palladium nanoparticles in a ceramic matrix using radiation grafting method  

NASA Astrophysics Data System (ADS)

Silicon carbide (SiC) ceramics containing palladium (Pd) nanoparticles were synthesized by the combination of the radiation grafting method, which allowed for uniform dispersion of Pd ions in polycarbosilane (PCS), and subsequent heat treatment, which was used to promote the bleedout phenomenon. The size and distribution of the Pd nanoparticles varied with the heat-treatment temperature. TEM and XRD analyses indicated that Pd nanoparticles of 2-5 nm in size were homogeneously distributed in the SiC ceramic matrix at temperatures lower than 1173 K. At a temperature of 1373 K, the size of these particles was found to increase and a portion of Pd was changed into Pd silicide. The Pd nanoparticles in samples heated at temperatures lower than 1173 K showed catalytic activity for hydrocarbon oxidation, whereas samples treated at 1373 K did not show any catalytic activity. These results suggest that Pd nanoparticles were formed on the SiC matrix at temperatures lower than 1173 K. The bleedout process enables the production of Pd nanoparticles as a combustion catalyst from radiation-grafted Pd-PCS.

Yoshimura, Kimio; Hakoda, Teruyuki; Sugimoto, Masaki; Yamamoto, Shunya; Yoshikawa, Masahito

2011-04-01

219

Synthesis of poly(N-isopropylacrylamide) hydrogels by radiation polymerization and cross-linking  

SciTech Connect

Poly(N-isopropylacrylamide) [poly(NIPAAm)] shows a typical thermal reversibility of phase transition in aqueous solutions. That is, it precipitates from solution above a critical temperature called the lower critical solution temperature (LCST) and dissolves below this temperature. When it is cross-linked, the obtained hydrogel collapses above LCST, while it swells and expands below LCST. This hydrogel has received much attention recently and has been used as a model system to demonstrate the validity of theories describing the coil-globule transition, swelling of networks, and folding and unfolding of biopolymers. It has also been proposed for various applications ranging from controlled drug delivery to solute separation. Poly(NIPAAm) hydrogel is usually synthesized at room temperature from an aqueous solution of the monomer by using a redox initiator composed of ammonium persulfate and N,N,N{prime},N{prime}-tetramethylethylenediamine in the presence of N,N{prime}-methylenebisacrylamide as a cross-linker. Since the LCST of poly(NIPAAm) is around 32 C, the polymerization at room temperature proceeds in a homogeneous solution. Recently, poly(NIPAAm) hydrogels were synthesized by starting the polymerization below the LCST and then elevating the temperature above it, by which method macroporous gels with fast temperature response were obtained. The idea is to apply a radiation--induced polymerization method for the synthesis of poly(NIPAAm) hydrogels. This method offers unique advantages for synthesis: it is a simple and additive-free process at all temperatures, and the degree of cross-linking can be easily controlled by irradiation conditions. Therefore, radiation methods are especially attractive for the synthesis of hydrogels with potential biomedical application where the residual chemical initiators may contaminate the product. It is possible to combine into one step the synthesis and sterilization of the product, and it is economically competitive.

Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi [Gunma Univ. (Japan). Dept. of Chemistry; Safranj, Agneza; Yoshida, Masaru; Omichi, Hideki [Japan Atomic Energy Research Inst., Gunma (Japan). Dept. of Material Development

1993-12-20

220

Temperature-controlled flow switching in nanocapillary array membranes mediated by poly(N-isopropylacrylamide) polymer brushes grafted by atom transfer radical polymerization.  

PubMed

We report actively controlled transport that is thermally switchable and size-selective in a nanocapillary array membrane (NCAM) prepared by grafting poly(N-isopropylacrylamide) (PNIPAAm) brushes onto the exterior surface of a Au-coated polycarbonate track-etched membrane. A smooth Au layer on the membrane surface, which is key to obtaining a uniform polymer film, was prepared by thermal evaporation of approximately 50 nm Au on both exterior surfaces. After evaporation, the inner diameter of the pore is reduced slightly, but the NCAM retains a narrow pore size distribution. PNIPPAm brushes with 10-30 nm (dry film) thickness were grafted onto the Au surface through surface-initiated atom transfer radical polymerization (ATRP) using a disulfide initiator, (BrC(CH3)2COO(CH2)11S)2. Molecular transport through the PNIPAAm polymer brush-modified NCAMs was investigated by real-time fluorescence measurements using fluorescein isothiocyanate (FITC)-labeled dextrans ranging from 4.4 to 282 kDa in membranes with variable initial pore diameters (80, 100, and 200 nm) and different PNIPAAm thicknesses. Manipulating the temperature of the NCAM through the PNIPAAm lower critical solution temperature (LCST) causes large, size-dependent changes in the transport rates. Over specific ranges of probe size, transport is completely blocked below the LCST but strongly allowed above the LCST. The combination of the highly uniform PNIPAAm brush and the monodisperse pore size distribution is critical in producing highly reproducible switching behavior. Furthermore, the reversible nature of the switching raises the possibility of using them as actively controlled filtration devices. PMID:17190519

Lokuge, Ishika; Wang, Xuejun; Bohn, Paul W

2007-01-01

221

Radiation-cured polymeric nanocomposites of enhanced surface-mechanical properties  

NASA Astrophysics Data System (ADS)

Though polymerisation-active metallo-organic nanoparticles have proven exceedingly efficient in modifying the viscoelastic properties of UV and EB crosslinked polymeric nanocomposites, they are obviously unsuitable for practical applications. Rather, adequate polymerisation-activity was imparted on inorganic nanoparticles, e.g. silica and alumina, by grafting onto them functionalised trialkoxysilanes, yielding covalent-bonded, hydrolysis-stable surface compounds. Extensive spectroscopic studies of their siloxane structure led to the idea of a core-shell nanocapsule. The polysiloxane shell formed around the inorganic nanoparticle is not only of major importance to the rheological behaviour of the nanodispersion but, moreover, also admits a sufficiently high nanofiller content for a pronounced reinforcement of the nanocomposite coating. In recent work, organophilation of the inorganic nanoparticles could be accomplished by just applying adsorptive means, thus evading the formation of the precarious alcohols and alkyl acrylates. In the event, round milled corundum micro-particles turned out to be efficient synergists in further improving the respective coatings.

Gläsel, H.-J.; Bauer, F.; Hartmann, E.; Mehnert, R.; Möbus, H.; Ptatschek, V.

2003-08-01

222

Preparation and characterization of fluorine-containing acrylate copolymers by 60Co ?-ray radiation co-polymerization  

Microsoft Academic Search

A series of fluorine-containing acrylate copolymers were prepared by 60Co ?-ray radiation co-polymerization in a mixed acrylate system, including butyl acrylate, acrylic acid, acrylonitrile, N-hydroxymethyl acrylamide and perfluoroalkylethyl methacrylate (FMA). The yield of the copolymers reached 96% when they were radiated for 34h with the radiation dose of 1kGy\\/h. Moreover, the surface structure and properties of the copolymers were determined

Jun Li; Qingjun Wang; Changhong Su; Qingmin Chen

2007-01-01

223

Gold-Loaded Polymeric Micelles for Computed Tomography-Guided Radiation Therapy Treatment and Radiosensitization  

PubMed Central

Gold nanoparticles (AuNPs) have generated interest as both imaging and therapeutic agents. AuNPs are attractive for imaging applications since they are nontoxic and provide nearly three times greater X-ray attenuation per unit weight than iodine. As therapeutic agents, AuNPs can sensitize tumor cells to ionizing radiation. To create a nanoplatform that could simultaneously exhibit long circulation times, achieve appreciable tumor accumulation, generate computed tomography (CT) image contrast, and serve as a radiosensitizer, gold-loaded polymeric micelles (GPMs) were prepared. Specifically, 1.9 nm AuNPs were encapsulated within the hydrophobic core of micelles formed with the amphiphilic diblock copolymer poly(ethylene glycol)-b-poly(?-capralactone). GPMs were produced with low polydispersity and mean hydrodynamic diameters ranging from 25 to 150 nm. Following intravenous injection, GPMs provided blood pool contrast for up to 24 h and improved the delineation of tumor margins via CT. Thus, GPM-enhanced CT imaging was used to guide radiation therapy delivered via a small animal radiation research platform. In combination with the radiosensitizing capabilities of gold, tumor-bearing mice exhibited a 1.7-fold improvement in the median survival time, compared with mice receiving radiation alone. It is envisioned that translation of these capabilities to human cancer patients could guide and enhance the efficacy of radiation therapy.

2013-01-01

224

Scale-up synthesis of vinyl polymer-grafted nano-sized silica by radical polymerization of vinyl monomers initiated by surface initiating groups in the solvent-free dry-system  

Microsoft Academic Search

For the purpose of the prevention of the environmental pollution and the simplification of reaction process, the scale-up radical graft polymerization of vinyl monomers onto nano-sized silica surface initiated by azo groups and peroxycarbonate groups previously introduced onto the surface in the solvent-free dry-system was investigated. The introduction of azo groups onto the silica surface was achieved by the reaction

Jun Ueda; Shimpei Sato; Asako Tsunokawa; Takeshi Yamauchi; Norio Tsubokawa

2005-01-01

225

Preparation of surface-imprinted polymer grafted with water-compatible external layer via RAFT precipitation polymerization for highly selective and sensitive electrochemical determination of brucine.  

PubMed

A novel brucine imprinted polymer was prepared on multi-walled carbon nanotubes by reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization. The polymer was further grafted with hydrophilic poly(glycerol monomethacrylate) brushes to improve its water-compatibility. The obtained molecularly imprinted material showed enhanced accessibility to brucine and improved selective recognition property in water medium. When the material was supported on an ionic liquid functionalized graphene coated glassy carbon electrode for the electrochemical determination of brucine, the resulting electrochemical sensor presented good analytical performance. Under the optimized conditions, the peak current was linear to brucine concentration in the ranges of 0.006-0.6 ?M and 0.6-5.0 ?M with sensitivities of 15.3 ?A/?Mmm(2) and 5.4 ?A/?M mm(2), respectively; the detection limit was 2 nM (S/N=3). The sensor was successfully applied to the determination of brucine in practical samples and the recovery for the standards added was 94-104%. PMID:24769450

Zhao, Lijuan; Zhao, Faqiong; Zeng, Baizhao

2014-10-15

226

Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies  

NASA Astrophysics Data System (ADS)

A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

Bach, Long Giang; Islam, Md. Rafiqul; Lee, Doh Chang; Lim, Kwon Taek

2013-10-01

227

A composite of polyelectrolyte-grafted multi-walled carbon nanotubes and in situ polymerized polyaniline for the detection of low concentration triethylamine vapor.  

PubMed

Multi-walled carbon nanotubes (MWNTs) grafted with sodium polystyrenesulfonate (NaPSS) were deposited on an interdigitated gold electrode decorated with a layer of positively charged poly(diallyldimethylammonium chloride) by a self-assembly method. Then polyaniline (PANI) was in situ polymerized on the surface of the MWNTs to prepare a composite. The structure and morphology of the composite were investigated by Raman spectroscopy and scanning electron microscopy. The electrical responses of the composite to triethylamine vapor of low concentrations were measured at room temperature. It was found that the composite exhibited a linear response to the vapor in the range of 0.5-8 ppm with the highest sensitivity of ?80%, which is much higher than that of MWNTs and PANI separately, and an obvious synergetic effect was observed. In addition, the detection limit was as low as the ppb level, and reversible and relatively fast responses (t(90%)?200 s and ?10 min for sensing and recovery, respectively) were observed. The sensing characteristics are highly related to the gas responses of PANI, and a sensing mechanism considering the interaction of MWNTs and PANI was proposed. PMID:21730534

Li, Yang; Wang, Huicai; Cao, Xiehong; Yuan, Minyong; Yang, Mujie

2008-01-01

228

A composite of polyelectrolyte-grafted multi-walled carbon nanotubes and in situ polymerized polyaniline for the detection of low concentration triethylamine vapor  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes (MWNTs) grafted with sodium polystyrenesulfonate (NaPSS) were deposited on an interdigitated gold electrode decorated with a layer of positively charged poly(diallyldimethylammonium chloride) by a self-assembly method. Then polyaniline (PANI) was in situ polymerized on the surface of the MWNTs to prepare a composite. The structure and morphology of the composite were investigated by Raman spectroscopy and scanning electron microscopy. The electrical responses of the composite to triethylamine vapor of low concentrations were measured at room temperature. It was found that the composite exhibited a linear response to the vapor in the range of 0.5-8 ppm with the highest sensitivity of ~80%, which is much higher than that of MWNTs and PANI separately, and an obvious synergetic effect was observed. In addition, the detection limit was as low as the ppb level, and reversible and relatively fast responses (t90%~200 s and ~10 min for sensing and recovery, respectively) were observed. The sensing characteristics are highly related to the gas responses of PANI, and a sensing mechanism considering the interaction of MWNTs and PANI was proposed.

Li, Yang; Wang, Huicai; Cao, Xiehong; Yuan, Minyong; Yang, Mujie

2008-01-01

229

Radiation-induced graft copolymerization of poly(ethylene glycol) monomethacrylate onto deoxycholate-chitosan nanoparticles as a drug carrier  

NASA Astrophysics Data System (ADS)

Poly(ethylene glycol) monomethacrylate-grafted-deoxycholate chitosan nanoparticles (PEGMA-g-DCCSNPs) were successfully prepared by radiation-induced graft copolymerization. The hydrophilic poly(ethylene glycol) monomethacrylate was grafted onto deoxycholate-chitosan in an aqueous system. The radiation-absorbed dose is an important parameter on degree of grafting, shell thickness and particle size of PEGMA-g-DCCSNPs. Owing to their amphiphilic architecture, PEGMA-g-DCCSNPs self-assembled into spherical core-shell nanoparticles in aqueous media. The particle size of PEGMA-g-DCCSNPs measured by TEM varied in the range of 70-130 nm depending on the degree of grafting as well as the irradiation dose. Berberine (BBR) as a model drug was encapsulated into the PEGMA-g-DCCSNPs. Drug release study revealed that the BBR drug was slowly released from PEGMA-g-DCCSNPs at a mostly constant rate of 10-20% in PBS buffer (pH 7.4) at 37 °C over a period of 23 days.

Pasanphan, Wanvimol; Rattanawongwiboon, Thitirat; Rimdusit, Pakjira; Piroonpan, Thananchai

2014-01-01

230

Preparation of thermosensitive membranes by radiation grafting of acrylic acid/ N-isopropyl acrylamide binary mixture on PET fabric  

NASA Astrophysics Data System (ADS)

Thermosensitive membranes were prepared by radiation-induced graft copolymerization of monomers on PET fabrics. A binary mixture of N-isopropyl acrylamide (NIPAAm) and acrylic acid (AA) was grafted on polyester fabric as a base material to introduce thermosensitive poly( N-isopropyl acrylamide) pendant chains having LCST slightly higher than 37 °C in the membrane. The influence of ferrous sulfate, radiation dose and monomer composition on the degree of grafting was studied. The structure of the grafted fabric was characterized by thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The thermosensitive nature of the fabric was monitored by swelling at different temperatures. The graft copolymerization of AA with NIPAAm enhanced the LCST of the resultant membrane to ˜37 °C. The moisture vapor transmission rate (MVTR) and air permeability of the fabric decreased slightly, may be due to the slight blocking of the fabric pores. The immobilization of tetracycline hydrochloride as the model drug and its release characteristics at different temperatures were monitored.

Gupta, Bhuvanesh; Mishra, Swaiti; Saxena, Shalini

2008-05-01

231

Characteristics of polymer microspheres prepared by radiation-induced polymerization in the presence of organic solvents  

NASA Astrophysics Data System (ADS)

Radiation-induced polymerization of diethylene glycol dimethacrylate (2G) was carried out in methyl orthoformate (MOF) in the range of 25 to -78°C, to obtain the polymeric microspheres. A transparent solution consisting of 2G and MOF showed an emulsified state after irradiation. This means that the colloidal particles of poly(2G)are deposited from monomer solution during the irradiation because of poor solubility. It was confirmed by microscopic observation that the shape of obtained polymer is composed of a complete sphere. The particle size of poly(2G) microsphere obtained by 10 kGy irradiation at temperatures of 25, 0 and -43°C was found to be 1.55±0.54, 1.75±1.09, and 1.76±1.21 ?m, respectively. No formation of the microsphere occurred when irradiated at -78°C. The preparation of poly(2G) microspheres was furter tried using various organic solvents under such conditions as 10 kGy and 25°C. According to this experiment, poly(2G) microspheres of the smallest size were obtained in the presence of ethyl caproate (0.70±0.25 ?m), while the largest size was obtained when tetrahydrofuran was used (8.61±4.21 ?m).

Yoshida, Masaru; Asano, Masaharu; Kaetsu, Isao; Morita, Yasushi

232

From Basic Biology to Randomized Clinical Trial: The Beta Radiation for ArterioVenous Graft Outflow Stenosis (BRAVO II)  

PubMed Central

The BRAVO-II study was a randomized controlled study of endovascular radiation therapy as compared to sham radiation therapy, following angioplasty of a thrombosed PRFE graft. The results did not show a benefit of endovascular radiation therapy, albeit in the context of an early termination of the study at less than 50% enrollment due to business reasons. Emphasis is laid on the fact that there may still be a role for radiation therapy in specific clinical settings associated with dialysis vascular access dysfunction.

Roy-Chaudhury, Prabir; Arnold, Perry; Seigel, Jeff; Misra, Sanjay

2013-01-01

233

Kinetics and characterization of radiation-induced grafting of styrene on fluoropolymers  

NASA Astrophysics Data System (ADS)

Grafting of styrene solution onto poly(ethylene-co-tetrafluoroethylene) (ETFE) was carried out by the pre-irradiation method. ETFE films were irradiated by 1.5 MeV electron beams in air. The influence of grafting temperature (50 to 80°C) has been investigated. It was found that the saturation grafting yield and the initial rate follow an Arrhenius law. The volume grafting yields were measured by FTIR spectroscopy in transmission and by weighing and the 'surface' grafting yields by FTIR-ATR. The results showed that grafting reaction is not monomer diffusion controlled in 30 ?m film, nevertheless heterogeneities are revealed. By in-situ ESR, the decay of peroxy radicals was recorded under various heating and grafting conditions. These experiments suggest that the peroxy radicals react rapidly with monomer, but do not initiate the grafting process. The propagating radicals were not detectable, which may indicate that polystyrene chains are very long.

Guilmeau, I.; Esnouf, S.; Betz, N.; Le Moël, A.

1997-08-01

234

The synthesis and characterization of hydroxyapatite-?-alanine modified by grafting polymerization of ?-benzyl-L-glutamate-N-carboxyanhydride.  

PubMed

In this study, hydroxyapatite (HAP) was surface-modified by the addition of ?-alanine (?-Ala), and the ring-opening polymerization of ?-benzyl-L-glutamate-N-carboxy-anhydride (BLG-NCA) was subsequently initiated. HAP containing surface poly-?-benzyl-L-glutamates (PBLG) was successfully prepared in this way. With the increase of PBLG content in HAP-PBLG, the solubility of HAP-PBLG increased gradually and it was ultimately soluble in chloroform. HAP-PLGA with surface carboxyl groups was obtained by the catalytic hydrogenation of HAP-PBLG. In the process of HAP modification, the morphology changes from rod to sheet and from flake to needle. The effect of BLG-NCA concentration on the character of hydroxyapatite-?-alanine-poly(?-benzyl-L-glutamate) (HAP-PBLG) was investigated. The existence of amino acids on the HAP surfaces was confirmed in the resulting Fourier transform infrared (FTIR) spectra. The resulting powder X-ray diffraction patterns indicated that the crystallinity of HAP decreased when the ratio of BLG-NCA/HAP-NH2 increased to 20/1. Transmission electron microscopy (TEM) indicated that the particle size of HAP-PBLG decreased significantly and that the resulting particles appeared less agglomerated relative to that of the HAP-NH? crystals. Furthermore, ¹H-NMR spectra and FTIR spectra revealed that hydroxyapatite-?-alanine-poly (L-glutamic acid) (HAP-PLGA) was able to successfully bear carboxylic acid groups on its side chains. PMID:24232735

Shan, Yukai; Qin, Yuyue; Chuan, Yongming; Li, Hongli; Yuan, Minglong

2013-01-01

235

Study of radiation-grafted FEP-G-polystyrene membranes as polymer electrolytes in fuel cells  

Microsoft Academic Search

Proton exchange membranes for fuel cell applications were synthesized by pre-irradiation grafting of styrene\\/divinylbenzene mixtures into poly(fluoroethylene-co-hexafluoropropylene) films and subsequent sulfonation. Grafting of pre-existing films overcomes the problem of shaping the grafted polymer into thin membranes and makes this process a potentially cheap and easy technique for the preparation of solid polymer electrolytes.The grafted membranes were characterized by measuring their

Felix N. Büchi; Bhuvanesh Gupta; Otto Haas; Günther G. Scherer

1995-01-01

236

Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization  

NASA Astrophysics Data System (ADS)

In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed.

Mahmudi, Naim; ?en, Murat; Güven, Olgun; Rendevski, Stojan

2007-04-01

237

Radiation tolerant polymeric films through the incorporation of small molecule dopants in the polymer matrix  

SciTech Connect

Radiation induced conductivity (RIC) in semicrystalline polyethylene terephthalate (PET) films can be reduced by incorporating small molecule electron traps into the polymer. The electron traps contained an aromatic core with strong electron withdrawing functionality pendant to the core and were incorporated into the PET film by immersing the polymer in a solution of dopant and solvent at elevated temperatures. The chemical functionality of the electron trapping molecule and the number of pendant functional groups had a strong impact on the equilibrium doping level and the most effective doping solvent. In addition, all of the electron traps exhibited effectiveness at reducing the RIC. The technique of incorporating small molecule dopants into the polymer matrix in order to reduce the RIC can potentially be exploited with other polymers films and coatings utilized in electronics devices such as encapsulants, conformal coatings, and polymeric underfills.

Lenhart, Joseph L.; Cole, Phillip J.; Cole, Shannon M.; Schroeder, John L.; Belcher, Michael E. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2008-01-15

238

Physico-chemical aspects of the drugs radiation sterilization in commercial packing (applied scientific problems of radiation pharmaceutical chemistry)  

SciTech Connect

The results of studies on the simultaneous radiosterilization of direct and bifurcational trachea prostheses made of silicon-organic rubber of soft elastic consistency, with polyethylenterephthalate and polyamid cuffs, and radiation chemical grafting of polymeric layer and linking with functional groups of the graft sulfanilamide and antibiotics layer are discussed. Radiopharmaceuticals are also described.

Safarov, S.A.

1993-12-31

239

Molecularly imprinted polymer membranes for substance-selective solid-phase extraction from water by surface photo-grafting polymerization.  

PubMed

Hydrophilized polyvinylidene fluoride microfiltration membranes were surface-modified in the presence of a template (terbumeton) in methanol with a graft copolymer of a functional monomer (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS, methacrylic acid, MAA, or acrylic acid, AA) and a cross-linker (N,N'-methylene-bis-acrylamide) using UV irradiation and benzophenone as photoinitiator. As result, membranes covered with a thin layer of imprinted polymer selective to terbumeton were obtained. Blank membranes were prepared with the same monomer composition, but in the absence of the template. The membranes' capacity to adsorb terbumetone from aqueous solution was evaluated yielding information regarding the effect of polymer synthesis (type and concentration of functional monomer, concentration of cross-linker) on the resulting membranes' recognition properties. UV spectroscopic studies of the interactions with terbumetone revealed that AMPS forms a stronger complex than MAA and AA. In agreement with that finding, imprinting with AMPS gave higher affinities than with MAA and AA. The terbumeton-imprinted membranes showed significantly higher sorption capability to this herbicide than to similar compounds (atrazine, desmetryn, metribuzine). With the novel surface modification technology, the low non-specific binding properties of the hydrophilized microfiltration membrane could successfully be combined with the receptor properties of molecular imprints, yielding substance-specific molecularly imprinted polymer composite membranes. The high affinity of these synthetic affinity membranes to triazine herbicides together with their straightforward and inexpensive preparation provides a good basis for the development of applications of imprinted polymers in separation processes such as solid-phase extraction. PMID:11217051

Sergeyev, T A; Matuschewski, H; Piletsky, S A; Bendig, J; Schedler, U; Ulbricht, M

2001-01-12

240

Measurements of the temperature dependence of radiation induced conductivity in polymeric dielectrics  

NASA Astrophysics Data System (ADS)

This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HN(TM) and Kapton E(TM)), polytetraflouroethylene (PTFE or Teflon(TM)), ethylene-tetraflouroethylene (ETFE or Tefzel(TM)), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at low incident dose rates of 0.01 rad/sec to 10 rad/sec. The steady-state RIC was found to agree well with the standard power law relation, sigmaRIC(D?) = kRIC(T) D?Delta(T) between conductivity, sigmaRIC and adsorbed dose rate, D?. Both the proportionality constant, kRIC, and the power, Delta, were found to be temperature-dependent above ~250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ~250 K, kRIC and Delta exhibited little change in any of the materials.

Gillespie, Jodie

241

Magnetic molecularly imprinted nanoparticles based on grafting polymerization for selective detection of 4-nitrophenol in aqueous samples.  

PubMed

In this study, an analytical procedure for the selective extraction and detection of 4-nitrophenol (4-NP) was investigated by using of molecularly imprinted polymer on the surface of magnetic nanoparticles (MNPs). The magnetic nanoparticles were modified by tetraethyl orthosilicate (TEOS) and 3-methacryloxypropyl trimethoxysilane (MPTS) before imprinting. The magnetic molecularly imprinted polymer (MMIP) was polymerized at the surface of modified MNPs by using of methacrylic acid (MAA) as functional monomer, 4-NP as template and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Experimental design by the Taguchi method was used for the optimization of synthesis procedure of imprinted polymer. The resulting MMIP showed high adsorption capacity, proper selectivity and fast kinetic binding for the template molecule. It was characterized by Fourier transform infrared (FT-IR) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The maximum adsorption capacity of MMIP was obtained as 57.8mgg(-1) and it took about 2h to achieve the equilibrium state. The adsorption curve of MMIP was also fitted with the Freundlich isotherm equation. The assay exhibited a linear range of 25-1000?gL(-1) for 4-NP with the correlation coefficient (R(2)) of 0.995. The method was also examined for the analysis of 4-NPs in seawater. For recovery evaluation, the seawater samples were spiked at two concentration levels of 50 and 100?gL(-1) of 4-NPs and the recovery values were in the range of 79.3-99.8%. The relative standard deviations (RSD) for the recoveries were less than 5.2%. PMID:23465129

Mehdinia, Ali; Baradaran Kayyal, Tohid; Jabbari, Ali; Aziz-Zanjani, Mohammad Ovais; Ziaei, Ehsan

2013-03-29

242

Adsorption of plasma proteins to DMAA hydrogels obtained by ionizing radiation and its relationship with blood compatibility  

Microsoft Academic Search

The interaction of plasma proteins such as albumin, ?-globulin, and fibrinogen with the surface of graft copolymers DMAA-G-PTFE, DMAA-G-PETFE, and DMAA-G-PE obtained by radiation graft polymerization was studied. The adsorption of serum proteins was affected by the hydrophilicity of the graft copolymers. Increased albumin adsorption and decreased fibrinogen and ?-globulin adsorption with increasing grafting levels was shown. A certain range

Alvaro A. A. De Queiroz; Sandra C. Castro; Olga Z. Higa

1997-01-01

243

Polymerization as a limiting factor for light product yields in radiation cracking of heavy oil and bitumen  

NASA Astrophysics Data System (ADS)

The kinetic model of radiation-thermal and low-temperature radiation cracking is developed subject to the specificity of radiation-induced processes and the effect of structure in extremely heavy hydrocarbon feedstock. Theoretical calculations are compared with the available experimental data. The dependences of the cracking product yields on temperature, dose and dose rate of ionizing irradiation are analyzed on the base of the developed model subject to the structural state of the feedstock. Radiation-induced polymerization and chemical adsorption are considered as the important factors limiting heavy oil conversion.

Zaikin, Yuriy A.; Zaikina, Raissa F.

2013-03-01

244

Preparation of strong acid cation-exchange membrane using radiation-induced graft polymerisation  

NASA Astrophysics Data System (ADS)

Polyethylene (PE) sheet modified with acrylic acid (AA) was grafted with p-vinyl benzene sulphonic acid sodium salt hydrate (SSS) using 60Co ?-rays in a direct grafting method in the presence of air at ambient temperature. It was observed that increasing dose results in increase of SSS grafting. Changes in surface area, thickness, ion-exchange capacity and water uptake with respect to dose were also evaluated. The grafting was confirmed by FTIR studies. The ion-exchange capacity of the grafted membrane under the conditions was 5.5-5.8 milli equivalent per gram (meq/g) which is better than most of the commercially available membranes.

Reddy, P. R. S.; Agathian, G.; Kumar, Ashok

2005-06-01

245

Radiation damage in patients treated by total-body irradiation, bone marrow grafting, and cyclosporin  

SciTech Connect

The bone marrow (BM) and peripheral blood (PB) from 63 patients were assessed for the presence of chromosomal aberrations after bone marrow transplantation (BMT) following total body irradiation (TBI) for leukemia. Forty-one patients showed no abnormalities in either BM or PB, and 22 had aberrations in either BM or PB or both. Only stable aberrations were found in the BM, but both stable and unstable abnormalities were present in the PB, the majority showing only unstable aberrations. Among the 25 patients who had a leukemic relapse, clonal chromosomal abnormalities were found in the BM of 12 out of the 16 cases for whom marrow was studied at the time of the relapse. A statistically significant negative correlation between leukemic relapse and graft versus host disease (GvHD) was found, but the relationships between chromosome damage and leukemic relapse, GvHD, and the pretransplant radiation dose and between the radiation dose and both leukemic relapse and GvHD were not significant.

Baker, M.C.; Lawler, S.D.; Harris, H.; Barrett, A.; Powles, R.L.

1986-03-01

246

Effects of ?-ray radiation grafting on aramid fibers and its composites  

NASA Astrophysics Data System (ADS)

Armos fiber was modified by Co 60 ?-ray radiation in the different concentrations' mixtures of phenol-formaldehyde and ethanol. Interlaminar shear strength (ILSS) was examined to characterize the effects of the treatment upon the interfacial bonding properties of Armos fibers/epoxy resin composites. The results showed that the ILSS of the composite, whose fibers were treated by 500 kGy radiation in 1.5 wt% PF, was improved by 25.4%. Nanoindentation technique analysis showed that the nanohardnesses of the various phases (the fiber, the interface and the matrix) in the composite, whose fibers were treated, were correspondingly higher than those in the composite, whose fibers were untreated. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectrum confirmed the increase in the polar groups at the fibers' surface. Atomic force microscopy (AFM) results revealed that the surface of the fibers treated was rougher than that of the fibers untreated. The wettability of the fibers' surface was also enhanced by the treatment. The conclusion that ?-ray irradiation grafting significantly improved the surface properties of Armos fibers could be drawn.

Zhang, Y. H.; Huang, Y. D.; Liu, L.; Cai, K. L.

2008-03-01

247

Microfiltration membranes prepared from polyethersulfone powder grafted with acrylic acid by simultaneous irradiation and their pH dependence  

NASA Astrophysics Data System (ADS)

Polyethersulfone (PES) powder was grafted with acrylic acid (AAc) by simultaneous ?-ray irradiation. The kinetics of the radiation induced graft polymerization was studied and the grafted PES powder was characterized. Then, microfiltration (MF) membranes were prepared from PES-g-PAAc powder with different degrees of grafting (DG) under phase inversion method. The swelling behavior and the mean pore size of MF membranes were measured, and the filtration property was tested. The results showed that the pore size and the flux of MF membranes increased with the increase in DG. And, MF membranes' properties were dependent on the pH value.

Deng, Bo; Li, Jingye; Hou, Zhengchi; Yao, Side; Shi, Liuqing; Liang, Guoming; Sheng, Kanglong

2008-07-01

248

Enhanced separation performance of PVDF/PVP-g-MMT nanocomposite ultrafiltration membrane based on the NVP-grafted polymerization modification of montmorillonite (MMT).  

PubMed

A novel hydrophilic nanocomposite additive (PVP-g-MMT), coupling of hydrophilic modifier, self-dispersant, and pore-forming agent (porogen), was synthesized by the surface modification of montmorillonite (MMT) with N-vinylpyrrolidone (NVP) via "grafting from" polymerization in the presence of H(2)O(2)-NH(3)·H(2)O as the initiator, and then the nanocomposite membrane of poly(vinylidene fluoride) (PVDF) and PVP-g-MMT was fabricated by wet phase inversion onto clean glass plates. The existence and dispersion of PVP-g-MMT had a great role on structures, morphologies, surface composition, and chemistry of the as-prepared nanocomposite membranes confirmed by varieties of spectroscopic and microscopic characterization techniques, all of which were the correlated functions of PVP-g-MMT content in casting solution. By using the dead-end filtration of protein aqueous solution, the performance of the membrane was evaluated. It was seen that all of the nanocomposite membranes showed obvious improvement of water flux and proper BSA rejection ratio, compared to the control PVDF membrane. Meanwhile, dynamic BSA fouling resistance and flux recovery properties were also greatly enhanced due to the changes of surface hydrophilicity and morphologies. All the experimental results indicated that the as-prepared PVDF nanocomposite membranes showed better separation performances than the control PVDF membrane. Hopefully, the demonstrated method of hydrophilic nanocomposite additive synthesis would be applied for commonly hydroxyl group-containing inorganic nanoparticles, which was favorable to fabricate hydrophilic nanoparticle-enhanced polymer membranes for water treatment. PMID:22376185

Wang, Panpan; Ma, Jun; Wang, Zhenghui; Shi, Fengmei; Liu, Qianliang

2012-03-13

249

The effects of radiation on the behavior of polymeric materials containing photoisomerizable groups  

SciTech Connect

The effects of ultraviolet and electron radiation on the behavior of polymeric materials containing photoisomerizable groups was examined with primary emphases on the development of photocontrollable gas separation membranes. These photoresponses were found to be reversible, suggesting a method for real-time control of membrane properties. Extruded, oriented polyethylene films containing photoisomerizable dyes contracted in length by as much as 4.5% upon exposure to ultraviolet light. A 12-70% recovery was observed after 20 minutes to 2 days in darkness. The photoresponse was attributed to the geometrical isomerism of the azo photochromes. Similarly, the effect of electron radiation on the behavior of uncoated poly(vinyl alcohol) containing phenylazobenzene side groups was investigated using scanning electron microscopy. The area of surface openings was reversibly decreased by as much as 45% as the emission current was increased. The stability of these uncoated materials under the electron beam was increased by the presence of the sodium salt of p-phenylazobenzoic acid. The effect of ultraviolet irradiation on the permeability and diffusivity of gases through nonporous membranes of ethyl cellulose and ethyl cellulose modified with p-phenylazobenzoyl chloride was examined at temperatures ranging from 30{degree} to 85{degree}C. Upon ultraviolet irradiation, the diffusion coefficient for nitrogen gas in membranes containing p-phenylazobenzoyl side groups reversibly decreased by as much as 18% with the maximum decrease observed at 40{degree}C. At 50{degree}C above, the irradiated and non-irradiated measurements were equivalent.

Hauenstein, D.E.

1989-01-01

250

Evaluation of the influence of homopolymerization on the removal of water-insoluble organics by grafted polypropylene fibers.  

PubMed

Lauryl acrylate (LA) grafted polypropylene (PP) fibers (PP-g-LA) were prepared via ultraviolet radiation and used to adsorb insoluble organics from aqueous solutions. The grafted fibers showed a maximum adsorption capacity of 18.85 g/g for benzene, while the adsorption capacity of the original PP fiber was only 8.21 g/g. However, graft polymerization is usually accompanied by the homopolymerization phenomenon, which is detrimental to practical applications of the grafted fiber. Homopolymerization negatively affected the adsorption capacities and the reusabilities of the grafted fibers, which decreased with increasing rates of homopolymerization. The adsorption capacity of grafted fiber with a homopolymerization rate of 18.40% was maintained above 85% of its initial adsorption capacity after being regenerated 10 times, while the adsorption capacity of the grafted fiber with a homopolymerization rate of 70.51% was approximately 40% of its initial capacity after 10 regenerations. PMID:22503098

Li, Shaoning; Wei, Junfu

2012-06-01

251

Swelling, ion uptake and biodegradation studies of PE film modified through radiation induced graft copolymerization  

NASA Astrophysics Data System (ADS)

An attempt to develop biodegradable polyethylene film grafting of mixture of hydrophilic monomers methacrylic acid (MAAc) and acrylamide (AAm) onto PE film has been carried out by preirradiation method using benzoyl peroxide as the radical initiator. Since ether linkages are susceptible to easy cleavage during degradation process, PE film was irradiated before the grafting reactions by ?-rays to introduce peroxidic linkages (PE-OO-PE) that offer sites for grafting. The effect of irradiation dose, monomer concentration, initiator concentration, temperature, time and amount of water on the grafting percent was determined. Maximum percentage of grafting of binary mixture (MAAc+AAm), (1792%) was obtained at a total concentration of binary monomer mixture=204.6×10 -2 mol/L ([MAAc]=176.5×10 -2 mol/L, [AAm]=28.1×10 -2 mol/L), [BPO]=8.3×10 -2 mol/L at 100 °C in 70 min. The grafted PE film was characterized by the Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopic (SEM) methods. Some selective properties of grafted films such as swelling studies, ion uptake and biodegradation studies have been investigated. The grafted films show good swelling in water, ion uptake studies shows promising results for desalination of brackish water and the soil burial test shows that PE film grafted with binary monomer mixture degrades up to 47% within 50 days.

Kaur, Inderjeet; Gupta, Nitika; Kumari, Vandna

2011-09-01

252

Cross-linked, ETFE-derived and radiation grafted membranes for anion exchange membrane fuel cell applications  

Microsoft Academic Search

To develop a series of cross-linked anion exchange membranes for application in fuel cells, poly(ethylene-co-tetrafluoroethylene) (ETFE) films was radiation grafted with vinyl benzyl chloride (VBC), followed by quaternization and crosslinking with 1,4-Diazabicyclo[2,2,2]octane (DABCO), alkylation with p-Xylylenedichloride (DCX), and quaternization again with trimethylamine (TMA). These anion exchange membranes were characterized in terms of water uptake, ion-exchange capacity, ionic conductivity as well

Jun Fang; Yi-xu Yang; Xiao-huan Lu; Mei-ling Ye; Wei Li; Yan-mei Zhang

253

Fabrication and mechanical characterization of biodegradable and synthetic polymeric films: Effect of gamma radiation  

NASA Astrophysics Data System (ADS)

Chitosan (1 wt%, in 2% aqueous acetic acid solution) and starch (1 wt%, in deionised water) were dissolved and mixed in different proportions (20-80 wt% chitosan) then films were prepared by casting. Tensile strength and elongation at break of the 50% chitosan containing starch-based films were found to be 47 MPa and 16%, respectively. It was revealed that with the increase of chitosan in starch, the values of TS improved significantly. Monomer, 2-butane diol-diacrylate (BDDA) was added into the film forming solutions (50% starch-based), then casted films. The BDDA containing films were irradiated under gamma radiation (5-25 kGy) and it was found that strength of the films improved significantly. On the other hand, synthetic petroleum-based polymeric films (polycaprolactone, polyethylene and polypropylene) were prepared by compression moulding. Mechanical and barrier properties of the films were evaluated. The gamma irradiated (25 kGy) films showed higher strength and better barrier properties.

Akter, Nousin; Khan, Ruhul A.; Salmieri, Stephane; Sharmin, Nusrat; Dussault, Dominic; Lacroix, Monique

2012-08-01

254

Plasma induced grafting of styrene onto nascent polyethylene powder  

Microsoft Academic Search

In this paper, the graft copolymers of styrene to nascent linear polyethylene reactor powders were prepared through plasma graft polymerization. The grafting reaction was initiated by the alkyl radicals formed on the surface of nascent polyethylene with plasma treatment as indicated by electron spin resonance spectra. In graft copolymerization by alkyl radicals, the grafting yield increased with either the plasma

Jun Tian; Xiao Lin; Baotong Huang; Jiping Xu

1995-01-01

255

Nature of yeast cells immobilized by radiation polymerization. Activity dependence on the water content of polymer carriers  

SciTech Connect

Higher activity of ethanol production due to higher density of yeast cells was observed in yeast cells immobilized with artificial polymer carriers of higher water content based on methoxypolyethyleneglycol methacrylate and 2-hydroxyethylacrylate. These polymer carriers were prepared by radiation-induced polymerization below 0 degrees C. Yeast cells were immobilized with these carriers by adsorption method during multiplication. Two possible reasons for higher activity were discussed. 10 references.

Fujimura, T.; Kaetsu, I.

1987-02-05

256

Optimization strategies for radiation induced grafting of 4-vinylpyridine onto poly(ethylene-co-tetraflouroethene) film using Box-Behnken design  

NASA Astrophysics Data System (ADS)

The radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(ethylene-co-tetrafluoroethene) (ETFE) was optimized using the Box-Behnken factorial design available in the response surface method (RSM). The optimized grafting parameters; absorbed dose, monomer concentration, grafting time and reaction temperature were varied in four levels to quantify their effect on the grafting yield (GY). The validity of the statistical model was supported by the small deviation between the predicted (GY=61%) and experimental (GY=57%) values. The optimum conditions for enhancing GY were determined at the following values: monomer concentration of 48 vol%, absorbed dose of 64 kGy, reaction time of 4 h and temperature of 68 °C. A comparison was made between the optimization model developed for the present grafting system and that for grafting of 1-vinylimidazole (1-VIm) onto ETFE to confirm the validly and reliability of the Box-Behnken for the optimization of various radiation induced grafting reactions. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to investigate the properties of the obtained films and provide evidence for grafting.

Mahmoud Nasef, Mohamed; Shamsaei, Ezzatollah; Ghassemi, Payman; Ahmed Aly, Amgad; Hamid Yahaya, Abdul

2012-04-01

257

Radiation-induced polymerization at high dose rate. IV. Chloroprene in bulk  

SciTech Connect

Bulk polymerization of chloroprene was studied at 25/sup 0/C in a wide dose rate range. Variations of the rate of polymerization (R/sub p/) and molecular weight as a function of dose rate were essentially the same as those in several monomers that are capable of radical and cationic polymerizations. The polymerization proceeds with radical mechanism at low dose rate and with radical and cationic mechanism concurrently at high dose rate. The number-average molecular weight of the high-dose-rate products was ca. 2400. Microstructure of the polymers was mainly of trans-1,4 unit with small fractions of cis-1,4 and 3,4-vinyl unit. Fractions of the vinyl unit and the inverted unit in trans-1,4 sequence which increased at high dose rate reflected the change of dominant mechanism of polymerization. 6 figures, 2 tables.

Hayashi, K.; Tachibana, M.; Okamura, S.

1980-11-01

258

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films  

NASA Astrophysics Data System (ADS)

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m2 day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1-5 kGy) and it was revealed that PS values were reduced significantly (p?0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1-1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1-5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p?0.05) with the rise of radiation dose.

Khan, Avik; Huq, Tanzina; Khan, Ruhul A.; Dussault, Dominic; Salmieri, Stephane; Lacroix, Monique

2012-08-01

259

Chemical and Radiation-Induced Grafting of p-Carboxy N-Phenyl Maleimide onto Chitosan  

Microsoft Academic Search

Chitosan was grafted with p-carboxy N-phenyl maleimide (PCPM) using a redox initiator potassium persulfate (K2S2O8) and sodium bisulfite (NaHSO3) and also by ? irradiation. The effects of monomer concentration, initiator concentration, pH value, and temperature on the extent of grafting were studied. The grafting percentage reached maximum at 1.0 mol\\/l monomer concentration and an initiator mixture ratio of 0.004:0.004 mol\\/l of K2S2O8:NaHSO3

Said S. Elkholy

2008-01-01

260

Polymeric Materials With Additives for Durability and Radiation Shielding in Space  

NASA Technical Reports Server (NTRS)

Polymeric materials are attractive for use in space structures because of their light weight and high strength In addition, polymers are made of elements with low atomic numbers (Z), primarily carbon (C), hydrogen (H), oxygen (0), and nitrogen (N) which provide the best shielding from galactic cosmic rays (GCR) (ref. 1). Galactic cosmic rays are composed primarily of nuclei (i.e., fully ionized atoms) plus a contribution of about 2% from electrons and positrons. There is a small but significant component of GCR particles with high charge (Z > 10) and high energy (E >100 GeV) (ref. 2). These so-called HZE particles comprise only 1 to 2% of the cosmic ray fluence but they interact with very high specific ionization and contribute 50% of the long- term dose to humans. The best shield for this radiation would be liquid hydrogen, which is not feasible. For this reason, hydrogen-containing polymers make the most effective practical shields. Moreover, neutrons are formed in the interactions of GCR particles with materials. Neutrons can only lose energy by collisions or reactions with a nucleus since they are uncharged. This is a process that is much less probable than the Coulombic interactions of charged particles. Thus, neutrons migrate far from the site of the reaction in which they were formed. This increases the probability of neutrons reaching humans or electronic equipment. Fast neutrons (> 1 MeV) can interact with silicon chips in electronic equipment resulting in the production of recoil ions which can cause single event upsets (SEU) in sensitive components (ref. 3). Neutrons lose energy most effectively by elastic collisions with light atoms, particularly hydrogen atoms. Therefore, hydrogen-containing polymers are not only effective in interacting with GCR particles; they are also effective in reducing the energy of the neutrons formed in the interactions.

Kiefer, Richard

2011-01-01

261

High-energy radiation monitoring based on radio-fluorogenic co-polymerization. I: small volume in situ probe  

NASA Astrophysics Data System (ADS)

A method of radiation dosimetry is described which is based on the radiation-induced initiation of polymerization of a bulk monomer (e.g. methyl methacrylate) containing a small concentration (about 100 ppm) of a compound which is non-fluorescent but which becomes highly fluorescent when it is incorporated into a growing polymer chain of the bulk monomer. We call the overall process 'radio-fluorogenic co-polymerization' or RFCP for short. The method is illustrated by results on the in situ monitoring of the accumulated dose within the irradiation chamber of a cobalt-60 gamma-ray source using a small plastic capsule containing about 0.2 ml of an RFCP solution. Remote monitoring of the fluorescence is carried out on a timescale of seconds using optical fibres connecting the probe to a 360 nm LED excitation source and a miniature spectrophotometer. The fluorescence is permanent and the intensity is linearly proportional to the accumulated dose from a few tenths of a gray up to hundreds of gray. The sensitivity to dose depends on the polymerizable monomer used and obeys a square root dependence on dose rate over the range studied, 0.27-3.76 Gy min-1. The polymeric nature of the fluorescent product suggests that the RFCP effect could be used to provide fixed two- or three-dimensional fluorescent images of dose deposition in gel films or phantoms.

Warman, J. M.; de Haas, M. P.; Luthjens, L. H.

2009-05-01

262

A gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters  

NASA Astrophysics Data System (ADS)

In this presentation we show results of investigations on gelatin-free dosimeters containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide (named Aqueous Polyacrylamide, APA, dosimeters). The dosimeters were prepared with three different total monomer concentrations (2, 6, and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all three dosimeters, show a continuous degree of polymerization over the range of dose 0.5 - 25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of cross-linked polymer formed at each dose. This model may be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

Babic, S.; Park, Y. S.; Schreiner, L. J.

2004-01-01

263

The 60Co- ? ray-initiated seeded-emulsion polymerization of methyl methacrylate in the presence of waterborne polyurethane seeds  

NASA Astrophysics Data System (ADS)

In this work, the waterborne polyurethane (WPU)/poly (methyl methacrylate) (PMMA) composite material was successfully prepared via 60Co- ? ray radiation-induced seeded emulsion polymerization. The kinetic curves of the synthesis of WPU have been obtained in MMA medium and in acetone medium, respectively. The FT-IR spectra were used to investigate the grafting efficiency of the PMMA on WPU backbone.

Zhang, Guixi; Zhang, Zhicheng

2004-09-01

264

Adsorption of Cr(VI) using cellulose microsphere-based adsorbent prepared by radiation-induced grafting  

NASA Astrophysics Data System (ADS)

Cellulose microsphere (CMS) adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto CMS followed by a protonation process. The FTIR spectra analysis proved that PDMAEMA was grafted successfully onto CMS. The adsorption of Cr(VI) onto the resulting adsorbent was very fast, the equilibrium adsorption could be achieved within 15 min. The adsorption capacity strongly depended on the pH of the solution, which was attributed to the change of both the existed forms of Cr(VI) and the tertiary-ammonium group of PDMAEMA grafted CMS with the pH. A maximum Cr(VI) uptake (ca. 78 mg g-1) was obtained as the pH was in the range of 3.0-6.0. However, even in strong acid media (pH 1.3), the adsorbents still showed a Cr(VI) uptake of 30 mg g-1. The adsorption behavior of the resultant absorbent could be described with the Langmuir mode. This adsorbent has potential application for removing heavy metal ion pollutants (e.g. Cr(VI)) from wastewater.

Li, Cancan; Zhang, Youwei; Peng, Jing; Wu, Hao; Li, Jiuqiang; Zhai, Maolin

2012-08-01

265

Acoustic radiation force impulse imaging for assessing graft fibrosis after pediatric living donor liver transplantation: a pilot study.  

PubMed

Graft fibrosis is a common finding during protocol biopsy examinations after pediatric liver transplantation. We evaluated the clinical utility of liver stiffness measurements by acoustic radiation force impulse (ARFI) imaging, a novel ultrasound-based elastography method, for assessing graft fibrosis after pediatric living donor liver transplantation (LDLT). We performed 73 liver stiffness measurements by ARFI imaging in 65 pediatric LDLT recipients through the upper midline of the abdomen (midline value) and the right intercostal space (intercostal value) around the time of protocol biopsy examinations. Fifty-nine of these liver stiffness measurements could be compared with histopathological findings. Graft fibrosis was assessed according to the degrees of portal and pericellular fibrosis. Significant fibrosis, which was defined as F2 or worse portal fibrosis and/or moderate or worse pericellular fibrosis, was observed in 14 examinations, which had significantly higher midline (P = 0.005) and intercostal values (P < 0.001) than the others. Liver stiffness measurements by ARFI imaging significantly increased with increases in the portal and pericellular fibrosis grades. For the diagnosis of significant fibrosis, the areas under the receiver operating characteristic curve (AUROCs) were 0.760 (P = 0.005) and 0.849 (P < 0.001) for the midline and intercostal values, respectively. The optimal cutoff values were 1.30 and 1.39 m/second for midline and intercostal values, respectively. Slight but significant elevations were noted in the results of biochemical liver tests: serum levels of ?-glutamyltransferase showed the highest AUROC (0.809, P = 0.001) with an optimal cutoff value of 20 IU/L. In conclusion, liver stiffness measurements by ARFI imaging had good accuracy for diagnosing graft fibrosis after pediatric LDLT. The pericellular pattern of fibrosis was frequently observed after pediatric LDLT, and moderate pericellular fibrosis was detectable by ARFI imaging. PMID:23894066

Tomita, Hirofumi; Hoshino, Ken; Fuchimoto, Yasushi; Ebinuma, Hirotoshi; Ohkuma, Kiyoshi; Tanami, Yutaka; Du, Wenlin; Masugi, Yohei; Shimojima, Naoki; Fujino, Akihiro; Kano, Motohiro; Fujimura, Takumi; Ishihama, Hideo; Shimizu, Takahiro; Tanabe, Minoru; Saito, Hidetsugu; Sakamoto, Michiie; Hibi, Toshifumi; Kitagawa, Yuko; Kuroda, Tatsuo

2013-11-01

266

Evaluation of Thermal Control Coatings and Polymeric Materials Exposed to Ground Simulated Atomic Oxygen and Vacuum Ultraviolet Radiation  

NASA Technical Reports Server (NTRS)

Numerous thermal control and polymeric samples with potential International Space Station applications were evaluated for atomic oxygen and vacuum ultraviolet radiation effects in the Princeton Plasma Physics Laboratory 5 eV Neutral Atomic Oxygen Facility and in the MSFC Atomic Oxygen Drift Tube System. Included in this study were samples of various anodized aluminum samples, ceramic paints, polymeric materials, and beta cloth, a Teflon-impregnated fiberglass cloth. Aluminum anodizations tested were black duranodic, chromic acid anodize, and sulfuric acid anodize. Paint samples consisted of an inorganic glassy black paint and Z-93 white paint made with the original PS7 binder and the new K2130 binder. Polymeric samples evaluated included bulk Halar, bulk PEEK, and silverized FEP Teflon. Aluminized and nonaluminized Chemfab 250 beta cloth were also exposed. Samples were evaluated for changes in mass, thickness, solar absorptance, and infrared emittance. In addition to material effects, an investigation was made comparing diffuse reflectance/solar absorptance measurements made using a Beckman DK2 spectroreflectometer and like measurements made using an AZ Technology-developed laboratory portable spectroreflectometer.

Kamenetzky, R. R.; Vaughn, J. A.; Finckenor, M. M.; Linton, R. C.

1995-01-01

267

The effect of additives on the enhancement of methyl methacrylate grafting to cellulose in the presence of UV and ionising radiation  

NASA Astrophysics Data System (ADS)

The role of various additives in the grafting of methyl methacrylate (MMA) to cellulose using UV and ionising radiation has been investigated. MMA grafting yields are hampered by competing homopolymerisation. The styrene comonomer technique was utilised to overcome this problem. The role of acid in these reactions has been studied as well as additives like, an inclusion compound (urea), thermal initiators and photoinitiators. Methanol was used as the swelling agent in all the experiments. Molecular weight studies with homopolymers indicate that both chemical and physical processes are involved in the mechanism of the reaction. The physical process involves a partitioning phenomenon whereas the chemical process concerns additional radical reactions in the radiation initiation step. This grafting mechanism is shown to be applicable to the simple radiation polymerisation of monomers in solution and also analogous UV fast curing systems.

Viengkhou, Visay; Ng, Loo-Teck; Garnett, John L.

1997-05-01

268

Synthesis of high-molecular-weight polymer of methyl chloride salt of N,N-dimethylaminoethyl methacrylate by radiation-induced polymerization at high pressure. [Gamma radiation  

SciTech Connect

Polymer of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate and its copolymer with acrylamide are used as cationic flocculants for the treatment of waste water containing organic suspensions. As reported, radiation-induced polymerization is one of the most convenient methods because of its temperature independence of initiation and extremely large G-value. In general, a flocculant with higher molecular weight has larger flocculation effects. The high-molecular-weight products were prepared in high monomer concentration and a low dose rate. This paper concerns the polymerization and copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate at high pressure, up to 7000 kg/cm/sup 2/, providing high-molecular-weight cationic flocculants.

Ishigaki, I.; Okada, T.; Sasuga, T.; Takehisa, M.; Machi, S.

1981-02-01

269

Introduction of anticoagulation group to polypropylene film by radiation grafting and its blood compatibility  

NASA Astrophysics Data System (ADS)

Based on in vitro tests for an improvement of the blood compatibility of polypropylene (PP) films by grafting O-butyrylchitosan (OBCS), we prepared a novel biocompatible film. The immobilization was accomplished by irradiating with ultraviolet light, OBCS being coated on the film surface to photolyze azide groups, thus cross-linking OBCS and PP together. The grafted sample films were verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA) and the water contact angle measurements. The blood compatibility of the OBCS-grafted PP films was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank PP film as the control. It demonstrated that blood compatibility of the OBCS-grafted surfaces is better than that of the blank PP. The suitable modifications could be carried out to tailor PP biomaterial to meet the specific needs of different biomedical applications. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new biomaterial in medical use.

Mao, Chun; Zhang, Can; Qiu, Yongzhi; Zhu, Aiping; Shen, Jian; Lin, Sicong

2004-04-01

270

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. V. Comparison with other surface treatments. [Gamma radiation  

SciTech Connect

Helium gas plasma treatment of low-density polyethylene (LDPE) yields much lower peel strength than oxidative treatment using chromic acid and oxygen gas plasma. The practical adhesion, the bondability retention, and the bond durability of oxidatively treated LDPE sheets, bonded with epoxy adhesives, have been compared with those of partially hydrolyzed LDPE-methyl acrylate surface grafts. The oxidized surfaces easily lose the bondability by light rubbing with tissue paper, solvent extraction, heat aging, and artificial weathering, whereas the grafted surfaces retain the bondability. The bondability loss is due to removal of the oxidized layer, and the bondability retention is due to retention of the surface homopolymer layer. Conventional antioxidants stabilize the grafted but not the oxidized surfaces against thermal oxidative degradation. The grafted LDPE joints have much higher bond durability in humid environments than those of the oxidized LDPE joints. The dry and wet peel strengths of oxidized LDPE joints are greatly improved by application of primers consisting of a base epoxy resin and organic solvents. An adhesion mechanism involving penetration of epoxy adhesives into the oxidized layers and subsequent reinforcement of the layers by curing of the penetrated epoxy is proposed. 5 figures, 5 tables.

Yamakawa, S.; Yamamoto, F.

1980-01-01

271

A mild method of amine-type adsorbents syntheses with emulsion graft polymerization of glycidyl methacrylate on polyethylene non-woven fabric by pre-irradiation  

NASA Astrophysics Data System (ADS)

A mild pre-irradiation method was used to graft glycidyl methacrylate (GMA) onto polyethylene (PE) non-woven fabric (NF). The polymer was irradiated by electron beam in air atmosphere at room temperature. The degree of grafting (Dg) was determined as a function of reaction time, absorbed dose, monomer concentration and temperature. After 30 kGy irradiation, with 5% GMA, surfactant Tween 20 (Tw-20) of 0.5% at 55 °C for 15 min, the trunk polymer was made grafted with a Dg of 150%. Selected PE-g-PGMA of different Dg was modified with aminated compounds such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA). The obtained amine-type adsorbents were prepared to remove copper and uranium ions from solution. It was shown that at least 90% of copper and 60% of uranium with the initial concentration from 3 to 1000 ppb can be removed from water.

Ma, Hongjuan; Yao, Side; Li, Jingye; Cao, Changqing; Wang, Min

2012-09-01

272

Preparation of chitosan\\/poly(butyl acrylate) hybrid materials by radiation-induced graft copolymerization based on phthaloylchitosan  

Microsoft Academic Search

Graft copolymerization of butyl acrylate onto chitosan via phthaloylchitosan intermediate has been examined. Because the intermediate phthaloylchitosan was soluble in organic solvents, the graft copolymerization can be carried out efficiently in homogeneous system. Under appropriate irradiation dose and concentration of butyl acrylate monomer, the grafting percentage reached 838%. The graft copolymers exhibited high swelling not only in aqueous acid but

Yu Li; Li Liu; Xiaofeng Shen; Yue-E. Fang

2005-01-01

273

Beta radiation in the treatment of in-stent restenosis of an in situ saphenous vein bypass graft A case report.  

PubMed

We describe a case of instent restenosis in a femoral-distal saphenous vein bypass graft successfully treated with brachytherapy. A 45-year-old insulin-requiring diabetic woman underwent an in-situ femoral-anterior tibial bypass graft for a non-healing ischemic ulcer. Despite a technically successful percutaneous transluminal angioplasty and endovascular stenting of a retained valve within the threatened graft, the wound failed to heal. At the 1-month follow-up, instent restenosis was documented and successful cutting balloon angioplasty, complemented by adjunctive beta-irradiation was successfully performed. Clinical and hemodynamic success was achieved, with prompt ulcer healing and intermediate-term graft patency maintained on surveillance duplex ultrasound follow-up. We review the literature on radiation therapy in the management of peripheral arterial disease and discuss therapeutic options in the management of restenosis. PMID:16263364

Lotun, Kapildeo; Soukas, Peter; Cho, Sung; O'Donnell, Kevin; Griben, André; Irwin, William T; Schainfeld, Robert M

2005-01-01

274

Development of novel hydrogels by modification of sterculia gum through radiation cross-linking polymerization for use in drug delivery  

NASA Astrophysics Data System (ADS)

In order to modify the sterculia gum polysaccharide, to develop the hydrogels meant for the drug delivery, we have prepared sterculia gum, 2-hydroxyethylmethacrylate (HEMA) and acrylic acid (AAc) based hydrogels by radiation-induced crosslinking polymerization. Polymeric networks (hydrogels) thus formed were characterized with SEMs, FTIR,TGA and swelling studies which were carried out as a function monomers concentration, radiation dose, amount of sterculia contents in the polymer matrix and nature of the swelling medium. This paper discusses the swelling kinetics of the hydrogels and release dynamics of anti-diarrhea model drug ornidazole from the hydrogels to evaluation of swelling and drug release mechanism. Diffusion exponent ' n' have 0.73, 0.56 and 0.61 values and gel characteristic constant ' k' have 1.28 × 10 -2, 2.95 × 10 -2 and 2.14 × 10 -2 values in distilled water, pH 2.2 buffer and pH 7.4 buffer. The release of drug from the polymer matrix occurred through non-Fickian diffusion mechanism. The values for the late time diffusion coefficients have been lower than the values of initial and average diffusion coefficients. It reflects that in the initial stages rate of release of drug from polymer matrix was higher as compared to the late stages, it means after certain time the drug release occurred in controlled manner.

Singh, Baljit; Vashishtha, Manu

2008-05-01

275

Preirradiation grafting of acrylonitrile onto polypropylene monofilament for biomedical applications: I. Influence of synthesis conditions  

NASA Astrophysics Data System (ADS)

Graft polymerization of acrylonitrile onto polypropylene (PP) monofilament was carried out by a preirradiation method using a 60Co gamma radiation source. The influence of synthesis conditions, such as preirradiation dose, reaction time, monomer concentration, reaction temperature and additives was determined. The grafting was considerably influenced by the instantaneous swelling of the monofilament in the reaction mixture during the course of the grafting process. The order of dependence of the rate of grafting on monomer concentration was found to be 1.04. The nature of the medium of the grafting and the additives had profound influence over the grafting reaction. The accelerative effects of solvent medium on the grafting were higher in methylethyl ketone (MEK) and dimethylformamide (DMF) as compared to methanol. At the same time, partial replacement of DMF with water led to acceleration in the grafting with peak maxima at 20% solvent composition. The addition of a small amount of sulfuric acid to the reaction mixture also resulted in a significant acceleration of the degree of grafting.

Gupta, Bhuvanesh; Jain, Rachna; Anjum, Nishat; Singh, Harpal

2006-01-01

276

An all-optical protocol to determine the molecular origin of radiation damage/enhancement in electro-optic polymeric materials  

NASA Astrophysics Data System (ADS)

Previous studies on the radiation effects upon polymer and polymer-based photonic materials suggest that the radiation resistance of the material is heavily dependent on the choice of polymer-host and guest-chromophore. To date, the best results have been achieved with electro optic polymeric materials based on CLD1 doped in APC, which has resulted in improved performance at the device level upon gamma-ray irradiation at moderate doses. However, the physical mechanisms are yet not fully understood. In this paper, we introduce an all-optical (linear and nonlinear) characterization protocol that is aimed to elucidate the mechanisms of the radiation damage/enhancement of electro-optic polymeric materials. This protocol is used to quantify the damage/enhancement effects upon irradiation in terms of the relevant physical parameters on a collection of electro-optic polymeric thin film samples.

Pérez-Moreno, Javier; Van Cleuvenbergen, Stijn; Vanbel, Maarten; Clays, Koen; Taylor, Edward W.

2012-10-01

277

Bulk polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane induced by gamma radiation  

NASA Astrophysics Data System (ADS)

Gamma ray-induced bulk polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane at ambient temperature has been investigated. It was found that the polymerization proceeds via a free radical mechanism through the reaction of vinyl groups, and the resulting polymer had a three-dimensional network structure. Kinetic features of the reaction were also studied, strong postpolymerization effects were observed at doses between 8 and 80 kGy. The composition of the sol fractions was determined by high pressure liquid chromatography, and the chemical structure of both the sol and gel fractions was analyzed by FTIR spectroscopy. Thermal stability of the gel fractions, determined by thermogravimetric analysis, and the thermomechanical behavior of unextracted samples were found to depend on the irradiation dose.

Alexandrova, Larissa; Diaz, Francisco; Canseco, Miguel; Likhatchev, Dmitri; Vera-Graziano, Ricardo

1998-01-01

278

High-energy radiation processing, a smart approach to obtain PVP-graft-AA nanogels  

NASA Astrophysics Data System (ADS)

Poly(N-vinylpyrrolidone)-grafted-acrylic acid biocompatible nanogels (NGs) were prepared using an exiting industrial-type electron accelerator and setups, starting from semi-dilute aqueous solutions of a commercial PVP and the acrylic acid monomer. As a result, NGs with tunable size and structure can be obtained quantitatively. Sterility was also imparted at the integrated dose absorbed. The chemical structure of the NGs produced was confirmed through Fourier Transformer Infrared Spectroscopy (FT-IR). The molecular and physico-chemical properties of NGs, such as the hydrodynamic dimensions and surface charge densities, for various polymer and monomer concentrations in the irradiated solutions, are discussed here.

Grimaldi, N.; Sabatino, M. A.; Przybytniak, G.; Kaluska, I.; Bondì, M. L.; Bulone, D.; Alessi, S.; Spadaro, G.; Dispenza, C.

2014-01-01

279

Controlled slow release of chemotherapeutic drugs for cancer from matrices prepared by radiation polymerization at low temperatures.  

PubMed

The vinyl polymer-chemotherapeutic agent composites of various shapes (rod, tablet, membrane, microsphere, and powder) were prepared by radiation polymerization at low temperatures for the purpose of durable controlled slow release of drugs from implanted matrices. Bleomycin hydrochloric acid, mitomycin C, and 5-fluorouracil were tested as chemotherapeutic drugs entrapped in poly(diethylene glycol dimethacrylate) including a small quantity of a polymer such as poly(styrene), poly(vinyl formal), poly(vinyl acetate), poly(methyl methacrylate) on polyethylene glycol No. 600. The release rates from the matrices depended much on the kind of polymer, drug, and monomer concentration in polymerization and also on the shape of the composite. The release of these drugs from polymer matrices obeyed the diffusion-controlled release mechanism based on Higuchi's equation and was durable for more than thirty days. It was found that the release rate can be controlled easily by design of the shapes and structures of the polymer matrices. PMID:6154055

Kaetsu, I; Yoshida, M; Yamada, A

1980-05-01

280

New trends of radiation processing applications  

NASA Astrophysics Data System (ADS)

Major fields of radiation processing applications are: polymeric materials, food processing, sterilization of medical products and environmental conservation. There are about 200 60Co gamma irradiation facilities and 700 electron beam accelerators, mainly for commercial purposes, throughout the world. Radiation cross-linking and grafting techniques of polymeric materials have been providing many unique products including heat materials, heat shrinkable materials, curing of coatings and battery separators. Extensive studies have been devoted to the development of bio-medical materials using radiation processing to prepare bio-compatible materials and controlled release of drugs. New wound dressings have been successfully developed in Poland and Israel for commercial clinical use.

Machi, Sueo

1996-03-01

281

Development of reinforced hydrogels — I. Radiation induced graft copolymerization of methylmethacrylate on non-woven polypropylene fabric  

Microsoft Academic Search

Polypropylene (PP) fibers were grafted with methylmethacrylate. Effects of direct and pre-irradiation method and monomer concentration on the degree of grafting were investigated. The grafted PP fibers were characterized by swelling measurements, IR spectroscopy and by its mechanical and thermal properties. It was found that the direct method was more efficient than the indirect or pre-irradiation method and the monomer

L. C Lopérgolo; L. H Catalani; L. D. B Machado; P. R Rela; A. B Lugão

2000-01-01

282

Investigation of space radiation effects in polymeric film-forming materials  

NASA Technical Reports Server (NTRS)

The literature search in the field of ultraviolet radiation effects that was conducted during the previous program, Contract No. NAS1-12549, has been expanded to include the effects of charged particle radiation and high energy electromagnetic radiation. The literature from 1958 to 1969 was searched manually, while the literature from 1969 to present was searched by using a computerized keyword system. The information generated from this search was utilized for the design of an experimental program aimed at the development of materials with improved resistance to the vacuum-radiation environment of space. Preliminary irradiation experiments were performed which indicate that the approaches and criteria employed are very promising and may provide a solution to the challenging problem of polymer stability to combined ultraviolet/high energy radiation.

Giori, C.; Yamauchi, T.; Jarke, F.

1975-01-01

283

Development of reinforced hydrogels — I. Radiation induced graft copolymerization of methylmethacrylate on non-woven polypropylene fabric  

NASA Astrophysics Data System (ADS)

Polypropylene (PP) fibers were grafted with methylmethacrylate. Effects of direct and pre-irradiation method and monomer concentration on the degree of grafting were investigated. The grafted PP fibers were characterized by swelling measurements, IR spectroscopy and by its mechanical and thermal properties. It was found that the direct method was more efficient than the indirect or pre-irradiation method and the monomer concentration for highest degree of grafting was 40% of MMA. Mechanical properties (tensile strength) and thermal stability decrease with grafting yield. Those changes were related to degradation of tie molecules between crystals and formation of rigid branches of PMMA on PP amorphous phase.

Lopérgolo, L. C.; Catalani, L. H.; Machado, L. D. B.; Rela, P. R.; Lugão, A. B.

2000-03-01

284

Preparation of chitosan/poly(butyl acrylate) hybrid materials by radiation-induced graft copolymerization based on phthaloylchitosan  

NASA Astrophysics Data System (ADS)

Graft copolymerization of butyl acrylate onto chitosan via phthaloylchitosan intermediate has been examined. Because the intermediate phthaloylchitosan was soluble in organic solvents, the graft copolymerization can be carried out efficiently in homogeneous system. Under appropriate irradiation dose and concentration of butyl acrylate monomer, the grafting percentage reached 838%. The graft copolymers exhibited high swelling not only in aqueous acid but also in organic solvents. Due to the poly(butyl acrylate) side chains, the resulting graft copolymers exhibited glass transition phenomena and showed improved thermal stability.

Li, Yu; Liu, Li; Shen, Xiaofeng; Fang, Yue-e.

2005-12-01

285

Optimization of reaction parameters of radiation induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetraflouroethene) using response surface method  

NASA Astrophysics Data System (ADS)

Radiation induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) was investigated. The grafting parameters such as absorbed dose, monomer concentration, grafting time and temperature were optimized using response surface method (RSM). The Box-Behnken module available in the design expert software was used to investigate the effect of reaction conditions (independent parameters) varied in four levels on the degree of grafting ( G%) (response parameter). The model yielded a polynomial equation that relates the linear, quadratic and interaction effects of the independent parameters to the response parameter. The analysis of variance (ANOVA) was used to evaluate the results of the model and detect the significant values for the independent parameters. The optimum parameters to achieve a maximum G% were found to be monomer concentration of 55 vol%, absorbed dose of 100 kGy, time in the range of 14-20 h and a temperature of 61 °C. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the properties of the obtained films and provide evidence for grafting.

Nasef, Mohamed Mahmoud; Aly, Amgad Ahmed; Saidi, Hamdani; Ahmad, Arshad

2011-11-01

286

Development of high-productivity, strong cation-exchange adsorbers for protein capture by graft polymerization from membranes with different pore sizes  

PubMed Central

This paper describes the surface modification of macroporous membranes using ATRP (atom transfer radical polymerization) to create cation-exchange adsorbers with high protein binding capacity at high product throughput. The work is motivated by the need for a more economical and rapid capture step in downstream processing of protein therapeutics. Membranes with three reported nominal pore sizes (0.2, 0.45, 1.0 ?m) were modified with poly(3-sulfopropyl methacrylate, potassium salt) tentacles, to create a high density of protein binding sites. A special formulation was used in which the monomer was protected by a crown ether to enable surface-initiated ATRP of this cationic polyelectrolyte. Success with modification was supported by chemical analysis using Fourier-transform infrared spectroscopy and indirectly by measurement of pure water flux as a function of polymerization time. Uniformity of modification within the membranes was visualized with confocal laser scanning microscopy. Static and dynamic binding capacities were measured using lysozyme protein to allow comparisons with reported performance data for commercial cation-exchange materials. Dynamic binding capacities were measured for flow rates ranging from 13 to 109 column volumes (CV)/min. Results show that this unique ATRP formulation can be used to fabricate cation-exchange membrane adsorbers with dynamic binding capacities as high as 70 mg/mL at a throughput of 100 CV/min and unprecedented productivity of 300 mg/mL/min.

Chenette, Heather C.S.; Robinson, Julie R.; Hobley, Eboni; Husson, Scott M.

2012-01-01

287

Effects of ?-ray radiation grafting on aramid fibers and its composites  

Microsoft Academic Search

Armos fiber was modified by Co60 ?-ray radiation in the different concentrations’ mixtures of phenol–formaldehyde and ethanol. Interlaminar shear strength (ILSS) was examined to characterize the effects of the treatment upon the interfacial bonding properties of Armos fibers\\/epoxy resin composites. The results showed that the ILSS of the composite, whose fibers were treated by 500kGy radiation in 1.5wt% PF, was

Y. H. Zhang; Y. D. Huang; L. Liu; K. L. Cai

2008-01-01

288

Radiation-grafted proton exchange membranes based on co-grafting from binary monomer mixtures into poly(ethylene-co-tetrafluoroethylene) (ETFE) film  

NASA Astrophysics Data System (ADS)

In this study, proton exchange membranes (PEMs) based on a poly(ethylene-co-tetrafluoroethylene) (ETFE) film were synthesized through the graft copolymerization of styrene and VTMS (vinyltrimethoxysilane), or styrene and TMSPM (3-(trimethoxysilyl) propyl methacrylate) binary monomer systems using a simultaneous irradiation method. The prepared membranes with the similar degrees of grafting were investigated by measuring ion exchange capacity, proton conductivity, water uptake, chemical stability, and dimensional stability. The results indicate that the silane-crosslinked proton exchange membrane (PEM) has not only lower water uptake and dimensional change but also high proton conductivity at low humidity condition compared to non-crosslinked poly(ethylene-co-tetrafluoroethylene)-g-poly(styrene sulfonic acid) (ETFE-g-PSSA). Also, the chemical stability of silane-crosslinked fuel cell membranes was more improved than that of non-crosslinked fuel cell membrane.

Sohn, Joon-Yong; Sung, Hae-Jun; Song, Joo-Myung; Shin, Junhwa; Nho, Young-Chang

2012-08-01

289

Surface modification of polyethylene by radiation-induced grafting for adhesive bonding. IV. Improvement in wet peel strength. [Gamma radiation  

SciTech Connect

Adhesive joints of hydrolyzed methyl acrylate grafts, bonded with epoxy adhesives, yield extremely high peel strength (adherend failure) in dry conditions. However, when the joints are exposed to humid environments, the peel strength rapidly decreases with exposure time and then reaches a constant value (wet peel strength). Since the locus of failure changes from the adherend to the homopolymer layer with decreasing peel strength, the decrease is due to a decrease in mechanical strength of the homopolymer layer itself, which results from its swelling by water absorption. Many attempts to reduce the swelling of the homopolymer layer or to strengthen the swollen homopolymer layer were unsuccessful except (1) priming with epoxy solutions consisting of a base epoxy resin and organic solvents which can dissolve not only epoxy resins but also hydrolyzed poly(methyl acrylate) and (2) partial etching of the homopolymer layer by photo-oxidative degradation. All the results on the improvement in wet peel strength can be explained in terms of the penetration of epoxy resins into the homopolymer layer and subsequent curing of the penetrated epoxy resin. 15 figures, 1 table.

Yamakawa, S.; Yamamoto, F.

1980-01-01

290

Performance of space durable polymeric nano composite under electromagnetic radiation at Low Earth Orbit  

Microsoft Academic Search

It is well known that during long mission at low Earth orbit (LEO) as well as geosynchronous Earth orbit (GEO), electromagnetic radiation such as proton, gamma rays, alpha particles etc. creates severe damages to space electronics equipment as well as structural materials of spacecraft. In this context, present study investigates the rationale to developing space materials which could be useful

S. Bhowmik; R. Benedictus

2007-01-01

291

Radiation-induced and RAFT-mediated grafting of poly(hydroxyethyl methacrylate) (PHEMA) from cellulose surfaces  

NASA Astrophysics Data System (ADS)

This paper presents the results of RAFT mediated free-radical graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a "grafting-from" approach under ?-irradiation. The effects of absorbed dose and monomer concentration on the graft ratios were investigated at different monomer (HEMA) to RAFT agent (cumyl dithiobenzoate, CDB) ratios. Cellulose-g-PHEMA copolymers with various graft ratios up to 92% (w/w) have been synthesized. The synthesized copolymers were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. The results of various techniques confirmed the existence of PHEMA in the copolymer composition.

Kodama, Yasko; Barsbay, Murat; Güven, Olgun

2014-01-01

292

Thermal analysis evaluation of mechanical properties changes promoted by gamma radiation on surgical polymeric textiles  

NASA Astrophysics Data System (ADS)

The large number of surgical operations with post-operative infection problems and the appearing of new infectious diseases, contribute to the development of new materials in order to answer the needs of health care services. This development must take into account the modifications promoted by sterilisation methods in materials, namely by gamma radiation. The differential scanning calorimetry (DSC) and thermogravimetry (TGA) techniques show that a nonwoven and a laminate textiles maintain a good molecular cohesion, do not showing high levels of degradation, for gamma radiation dose values lower than 100 kGy in nonwoven and 200 kGy in laminate materials. The tensile strength and the elongation decrease slowly for the nonwoven textile and decrease faster for the laminate textile for 25 and 80 kGy absorbed dose. This paper shows that the DSC and TGA techniques can be helpful for the prevision of mechanical changes occurred in the materials as a consequence of the gamma irradiation.

Ferreira, L. M.; Casimiro, M. H.; Oliveira, C.; Cabeço Silva, M. E.; Marques Abreu, M. J.; Coelho, A.

2002-05-01

293

Uranium Sorption by Pseudomonas Biomass Immobilized in Radiation Polymerized Polyacrylamide Bio-Beads  

Microsoft Academic Search

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium

S. F. DSOUZA; PINAKI SAR; SUFIA K. KAZY; B. S. KUBAL

2006-01-01

294

Influence of ?-ray radiation grafting on interfacial properties of aramid fibers and epoxy resin composites  

Microsoft Academic Search

This research used Co ?-ray radiation to modify Armos fibers in 1,2-epoxy-3-chloropropane. After the treatment, the interlaminar shear strength (ILSS) values of aramid\\/epoxy composites were improved by about 20%. Surface elements of Armos fibers were determined by XPS analysis, which indicated that the oxygen\\/carbon ratio was increased. The surface of the fibers treated was rougher than that of the untreated

Yanhua Zhang; Yudong Huang; Jinmei He; Lina Wu; Zhiwei Xu

2008-01-01

295

Synthesis of chemically cross-linked polyvinyl alcohol-co-poly (methacrylic acid) hydrogels by copolymerization; a potential graft-polymeric carrier for oral delivery of 5-fluorouracil  

PubMed Central

Background of the Study The propose of the present work was to develop chemically cross-linked polyvinyl alcohol-co-poly(methacrylic acid) hydrogel (PVA-MAA hydrogel) for pH responsive delivery of 5-Fluorouracil (5-FU). Methods PVA based hydrogels were prepared by free radical copolymerization. PVA has been cross-linked chemically with monomer (methacrylic acid) in aqueous medium, cross-linking agent was ethylene glycol di-methacrylate (EGDMA) and benzoyl peroxide was added as reaction initiator. 5-FU was loaded as model drug. FTIR, XRD, TGA and DSC were performed for characterization of copolymer. Surface morphology was studied by SEM. pH sensitive properties were evaluated by swelling dynamics and equilibrium swelling ratio at low and higher pH. Results FTIR, XRD, TGA and DSC studies confirmed the formation of new copolymer. Formulations with higher MAA contents showed maximum swelling at 7.4 pH. High drug loading and higher drug release has been observed at pH 7.4. Conclusions The current study concludes that a stable copolymeric network of PVA was developed with MAA. The prepared hydrogels were highly pH responsive. This polymeric network could be a potential delivery system for colon targeting of 5-FU in colorectal cancers.

2013-01-01

296

Synthesis and characterization of psyllium-NVP based drug delivery system through radiation crosslinking polymerization  

NASA Astrophysics Data System (ADS)

In order to develop the hydrogels meant for the drug delivery, we have prepared psyllium- N-vinylpyrrolidone (NVP) based hydrogels by radiation induced crosslinking. Polymers were characterized with SEMs, FTIR and swelling studies. Swelling of the hydrogels was studied as a function of monomer concentration, total radiation dose, temperature, pH and [NaCl] of the swelling medium. The swelling kinetics of the hydrogels and release dynamics of anticancer model drug (5-fluorouracil) from the hydrogels have been carried out for the evaluation of swelling and drug release mechanism. It has been observed that diffusion exponent ' n' have 0.8, 0.9, 0.8 and gel characteristics constant ' k' have 9.22 × 10 -3, 2.06 × 10 -3, 11.72 × 10 -3 values for the release of drug from the drug loaded hydrogels in distilled water, pH 2.2 buffer and pH 7.4 buffer, respectively. The present study shows that the release of drug from the hydrogels occurred through Non-Fickian diffusion mechanism.

Singh, Baljit; Kumar, S.

2008-08-01

297

Radiation-induced degradation of polymeric spacecraft materials under protective oxide coatings  

NASA Astrophysics Data System (ADS)

We report the results of experiments, in which two SiO 2-coated polymers (Kapton ® polyimide, and Mylar ® polyester), and ITO-coated Kapton ® are exposed to high-energy radiation. Possible modification or damage of the coating-polymer interface is assessed by adhesive testing, using a CSEM MicroScratch tester, with which we measure the "critical load" ( Lc) for coating delamination from the polymer surface, and by microscopy, compared with untreated witness samples. We deposit thin (sub-?m) coatings of SiO 2 by plasma-enhanced chemical vapor deposition (PECVD), in order to obtain strong (chemical) bonding at the substrate/coating interface. 100 keV protons and a hydrogen microwave plasma "lamp" with an MgF 2 window at a power density of 125 ?W cm -2 are used to irradiate the sample surfaces.

Lachance, J.; Co??a, C.; Fozza, A. C.; Czeremuszkin, G.; Houdayer, A.; Wertheimer, M. R.

2001-12-01

298

Postgrafting of vinyl polymers onto hyperbranched poly(amidoamine)-grafted nano-sized silica surface  

Microsoft Academic Search

To prepare polymer-grafted nano-sized silica with hydrophilic core and hydrophobic shell and with higher percentage of grafting, the postgraft polymerization of vinyl polymers onto hyperbranched poly(amidoamine)-grafted (PAMAM-grafted) nano-sized silica initiated by the system consisting of Mo(CO)6 and terminal trichloroacetyl groups of PAMAM-grafted silica was investigated. The introduction of trichloroacetyl groups onto PAMAM-grafted silica surfaces was readily achieved by the reaction

Yoshinao Taniguchi; Kumi Shirai; Hiroshi Saitoh; Takesi Yamauchi; Norio Tsubokawa

2005-01-01

299

Radiation synthesis of multifunctional polymeric hydrogels for oral delivery of insulin.  

PubMed

Polyelectrolyte crosslinked hydrogel was synthesized using gamma radiation-induced copolymerization of methacrylic acid (MAA), N,N-dimethyl aminoethyl methacrylate (DMAEMA) in aqueous solution to utilize for oral delivery of insulin. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion in the glassy polymer was discussed. In addition, the swelling kinetics tests on MAA/DMAEMA (90/10) reveal that the swelling kinetics of the proposed hydrogel follows a Fickian diffusion process in media of pH 5, and an anomalous diffusion process in media of pH 1.5 and 7.2. The cross-linked three-dimensional polymers were characterized by scanning electron microscopy and FT-IR. In the matrices with increase in the content of MAA had shown increased bioadhesivity. Insulin was entrapped in these gels and the in vitro release profiles were established separately in both (SGF, pH 1.5) and (SIF, pH 7.2). The release profile of insulin showed negligible release in acidic media (SGF, pH 1.5) and sustained release in simulated intestinal fluid (SIF, pH 7.2). Drug release studies showed that the increasing content of MAA in the copolymer enhances release in SIF to design and improve insulin release behavior from these carriers. PMID:24055698

Abou Taleb, Manal F

2013-11-01

300

Prevention of graft rejection in allogeneic bone marrow transplantation. II. Preclinical studies with three radiation protocols  

SciTech Connect

Three radiotherapeutic regimens were compared in vitro to determine their immunosuppressive potential against non-MHC-restricted cytotoxic cells. Assays of natural killer and lymphokine-activated killer function, and cytotoxicity against allogeneic cells were used to quantitate the cytotoxic potential of peripheral blood mononuclear cells from healthy individuals following irradiation with a single dose of 1000 cGy on day 0, 1320 cGy of fractionated radiation (165 cGy b.i.d. x 4 days), or split-dose irradiation consisting of 1000 cGy on day 0 followed 5 or 7 days later by 500 cGy. Both irradiated and nonirradiated (control) PBMC cultures were maintained in culture with medium containing interleukin-2, immunophenotyped, and assayed for cytotoxicity from 1 to 8 days after irradiation. Single dose and fractionated-dose irradiation resulted in a progressive decline in cytotoxic capacity, with an 80% inhibition of both NK and LAK cell activity 8 days after onset of irradiation. The split dose of 500 cGy administered 7 days after a dose of 1000 cGy was found to be the most effective in eliminating NK (93% inhibition) and LAK (100% inhibition) cytotoxicity. These data indicate that split-dose irradiation may result in greater immunosuppression than single-dose or fractionated irradiation.

Malilay, G.P.; Sevenich, E.A.; Filipovich, A.H. (Univ. of Minnesota, Minneapolis (USA))

1990-09-01

301

Neural Grafts Attenuate Behavioral Deficits Produced by Early Radiation-Induced Hypoplasia of Fascia dentata Granule Cells.  

National Technical Information Service (NTIS)

A growing literature suggests that brain injuries, once believed to be irreversible, may now be successfully treated through the use of techniques involving neural transplantation of embryonic brain tissue. Such grafts typically exhibit growth, long-term ...

G. A. Mickley J. L. Ferguson T. J. Nemeth M. A. Mulvihill

1990-01-01

302

Temperature-responsiveness and biocompatibility of DEGMA/OEGMA radiation-grafted onto PP and LDPE films  

NASA Astrophysics Data System (ADS)

Polypropylene (PP) and low density polyethylene (LDPE) were modified by ?-ray grafting of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA300 or OEGMA475 with Mn 300 and 475 respectively) with different monomer concentrations and mol ratios. The grafting percentage was evaluated as a function of the solvent, irradiation dose, reaction time, temperature, and monomers concentration. The grafted materials were more hydrophilic than the pristine polymers, as observed by contact angle and swelling in water. Temperature-responsive behavior was evaluated using DSC showing transitions between 34 and 48 °C. In vitro hemocompatibility, protein adsorption, cytotoxicity and bacteria adhesion tests were also carried out. Overall, the DEGMA/OEGMA grafting provides hemo and cytocompatible materials that exhibit temperature-responsive hydrophilic features and decreased protein adsorption.

Ramírez-Jiménez, Alejandro; Alvarez-Lorenzo, Carmen; Concheiro, Angel; Bucio, Emilio

2014-06-01

303

Temperature-sensitive porous membrane production through radiation co-grafting of NIPAAm on/in PVDF porous membrane  

NASA Astrophysics Data System (ADS)

N-isopropylacrylamide (NIPAAm) monomer was grafted on and in poly(vinylidene fluoride) (PVDF) micro-pore membrane by ?-irradiation. The influence of irradiation and reaction conditions on the grafting yield was investigated in detail. The chemical structure of NIPAAm-grafted PVDF (NIPAAm-g-PVDF) membrane was characterized by Fourier transform infrared spectra and X-ray photoelectron spectra measurements. The morphology of the sample surface as well as the cross-section before and after grafting was characterized by scanning electron microscope. The temperature sensitive properties of the membrane were monitored by measuring the conductance as well as the water flux through the sample thickness. The results show that the membrane exhibits clearly temperature-sensitive permeability to water as expected, i.e. the permeability of water changes dramatically as the temperature goes over the lower critical solution temperature of NIPAAm.

Liu, Qi; Zhu, Zhiyong; Yang, Xiaomin; Chen, Xiliang; Song, Yufeng

2007-04-01

304

Surface modification of polymeric microspheres using glycopolymers for biorecognition  

Microsoft Academic Search

We report the synthesis and characterization of sugar-containing microspheres consisting of poly(divinylbenzene) (PDVB) cores onto which chains of galactose- or mannose-bearing polymers have been grafted. PDVB particles prepared by distillation polymerization with a diameter of 2.4?m containing residual surface vinyl groups were used as starting material. “Grafting from”, “grafting through” and “grafting to” techniques were performed and special interest was

André Pfaff; Leonie Barner; Axel H. E. Müller; Anthony M. Granville

2011-01-01

305

Controlled release of 5-fluorouracil or mitomycin-c from polymer matrix: Preparation by radiation polymerization and in vivo evaluation of the anticancer drug/polymer composites  

NASA Astrophysics Data System (ADS)

Polymer tablets containing anticancer drugs such as 5-fluorouracil (5-FU) and mitomycin-C (MMC) have been prepared to evaluate the drug-release characteristics in vitro and the effect on local control of mouse solid tumors in vivo. Radiation-induced polymerization of hydrophilic monomers (2-hydroxyethyl methacrylate and related monomers) at low temperature (-80°C) was performed to immobilize 5-FU or MMC in the polymer matrix. The drug was dispersed as microcrystallines within the polymer matrix. The rate of drug release in vitro in buffer solution (pH7.0, 37°C) increased with increase in hydrophilicity of polymer matrix. Appropriate amount of crosslinks within the polymer matrix, as formed by ethylene glycol dimethacrylate (2G) added in the polymerization system, was effective to control the rate of drug release. The drug release became faster upon the addition of increasing amount of water in the radiation-induced polymerization. The tablet consisting of drug/polymer was buried surgically near solid tumors of striate muscle sarcoma (S180) transplanted to Kunming mice and the therapeutic effect of slow releasing drugs was evaluated in vivo by reference to intraperitoneal (i.p.) injection of the corresponding drugs. The slow releasing drugs led to high chemotherapeutic gain for local control of solid tumors with remarkable reduction of toxic side effect of the drugs.

Li, Ximing; Shen, Weiming; Liu, Chengjie; Nishimoto, Sei-Ichi; Kagiya, Tsutomu

306

Bloch surface waves-controlled fluorescence emission: Coupling into nanometer-sized polymeric waveguides  

NASA Astrophysics Data System (ADS)

The lateral confinement of Bloch surface waves on a patterned multilayer is investigated by means of leakage radiation microscopy (LRM). Arrays of nanometric polymeric waveguides are fabricated on a proper silicon-nitride/silicon-oxide multilayer grown on a standard glass coverslip. By exploiting the functional properties of the polymer, fluorescent proteins are grafted onto the waveguides. A fluorescence LRM analysis of both the direct and the Fourier image plane reveals that a substantial amount of emitted radiation couples into a guided mode and then propagates into the nanometric waveguide. The observations of the mode are supported by numerical simulations.

Ballarini, Mirko; Frascella, Francesca; Enrico, Emanuele; Mandracci, Pietro; De Leo, Natascia; Michelotti, Francesco; Giorgis, Fabrizio; Descrovi, Emiliano

2012-02-01

307

Preparation of a new micro-porous poly(methyl methacrylate)-grafted polyethylene separator for high performance Li secondary battery  

NASA Astrophysics Data System (ADS)

In this study, micro-porous poly(methyl methacrylate)-grafted polyethylene separators (PE-g-PMMA) were prepared by a radiation-induced graft polymerization of methyl methacrylate onto a conventional PE separator followed by a phase inversion. After the phase inversion, the micro-pores were generated in the grafted PMMA layer. The prepared micro-porous PE-g-PMMA separators showed an improved electrolyte uptake and ionic conductivity due to their improved affinity with a liquid electrolyte and the presence of pores in the grafted PMMA layer. The PE-g-PMMA separators exhibited a lower thermal shrinkage compared to the original PE separator. The PE-g-PMMA separators showed a better oxidation stability up to 5.0 V when compared to the original PE separator (4.5 V).

Gwon, Sung-Jin; Choi, Jae-Hak; Sohn, Joon-Yong; Ihm, Young-Eon; Nho, Young-Chang

2009-10-01

308

Physical properties of agave cellulose graft polymethyl methacrylate  

NASA Astrophysics Data System (ADS)

The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm-1 which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan

2013-11-01

309

Engineering Polymeric Scaffolds for Bone Grafts  

Microsoft Academic Search

Orthopedic injuries resulting from trauma or improper development often require surgical intervention to restore natural tissue function. Currently, over one million operations are performed annually for the surgical reconstruction of bone [50]. The well-known limitations associated with autografts, allografts, and bone cements have led to the investigation of synthetic polymers as support matrices for bone tissue engineering. Polymers are long-chain

Martha W. Betz; Diana M. Yoon; John P. Fisher

310

Water-Soluble Polymers Via an Outwardly Dry Polymerization Process.  

National Technical Information Service (NTIS)

This patent application relates to a method which involves graft polymerizing water-soluble monomers with starch under conditions which are outwardly dry appearing. Conversion of monomer to polymer is nearly quantitative; and, since excess water is not pr...

G. F. Fanta R. C. Burr

1975-01-01

311

Nanofiltration membrane prepared from cardo polyetherketone ultrafiltration membrane by UV-induced grafting method  

Microsoft Academic Search

Hydrophilic nanofiltration membranes were prepared by graft polymerization of hydrophilic monomers onto the surface of ultrafiltration membranes made from cardo polyetherketone (PEK-C). The method consists of a UV irradiation in the presence of acrylic for an in situ graft polymerization of polyacrylic acid (PAA) on the surface of the UF membranes. The effect of UV intensity, irradiation time and monomer

Changquan Qiua; Fan Xu; Quang Trong Nguyenb; Zhenghua Ping

312

Production of monodisperse, polymeric microspheres  

NASA Technical Reports Server (NTRS)

Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

1990-01-01

313

Synthesis and characterization of radiation grafted films for removal of arsenic and some heavy metals from contaminated water  

NASA Astrophysics Data System (ADS)

Grafting of styrene/maleic anhydride and methyl methacrylate/maleic anhydride binary monomers onto the low density polyethylene film was performed using the ?-ray irradiation technique. Then, the synthesized grafted films were treated with different ammonia derivatives for developing chelating functionalization. These chelating products were characterized by the gravimetric method as well as by the Fourier transformed infrared spectroscopic method, and were used for removal of arsenic and some heavy metals from aqueous solutions. The optimum absorbed dose of 30 kGy reveals the graft yielding of about 325% in the films. Uptake of arsenic and some heavy-metal ions (Cr(III), Mn(II), Fe(III), Ni(II), Cu(II) and Pb(II)) from contaminated water by the chelating functionalized films (CFF) was examined by an atomic absorption spectrophotometer. The maximum arsenic removal capacity of 5062 mg/kg has been observed for the film treated with hydroxylamine hydrochloride. The CFF prepared by semicarbazide and thiol analogs show affinity toward the metal ions with an order: Cu(II)>Fe(III)>Mn(II) etc. The results obtained from this study indicate that the functionalized films show good chelating and ion-exchange property for metal ions.

Chowdhury, M. N. K.; Khan, M. W.; Mina, M. F.; Beg, M. D. H.; Khan, Maksudur R.; Alam, A. K. M. M.

2012-10-01

314

Polymeric Gel Electrolytes for Electrochemical Capacitors  

Microsoft Academic Search

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and\\/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of

Masayuki Morita; Jin-Li Qiao; Naoki Ohsumi; Nobuko Yoshimoto; Minato Egashira

2006-01-01

315

Graft apparatus  

US Patent & Trademark Office Database

Stents and methods of using stents are provided. Stents of the invention provide external support structure for a blood vessel segment disposed within, wherein the stents are capable of resilient radial expansion in a manner mimicking the compliance properties of an artery. The stent may be formed of a knitted or braided mesh formed so as to provide the needed compliance properties. A venous graft with the stent and a vein segment disposed within is provided, wherein graft is capable of mimicking the compliance properties of an artery. Methods of selecting stents for downsizing and methods of using the stents of the invention in downsizing and smoothening are provided. Methods of replacing a section of an artery with a venous graft including a stent of the invention are provided. Methods of reducing intimal hyperplasia in implanted vein segment in a venous graft using stents of the invention are provided.

2014-06-10

316

Thermosensitive Behavior of Poly(N-isopropylacrylamide) Grafted Polystyrene Nanoparticles  

Microsoft Academic Search

W ea nalyzed the thermosensitive behavior of monodisperse polystyrene (PSt) nanoparticles having differen td ensities and chain lengths of grafted poly( N-isopropylacrylamide) (PNIPAAm) on their surfaces. The PSt nanoparticles were synthesized by free radical copolymerization of styrene monomer with PNIPAAm macromonomers in mixed ethanol\\/water solvents. The grafted PNIPAAm densities on the PSt nanoparticle surfaces can be controlled by varying polymerization

Ming-Qing CHEN; Takeshi SERIZAWA; Chi WU; Mitsuru AKASHI

2003-01-01

317

Olefin polymerization  

SciTech Connect

This patent describes a process for polymerizing an alpha-olefin, it comprises: contacting the alpha-olefin under polymerization conditions with a catalytic amount of a catalyst system comprising a catalyst produced by contacting an inorganic lanthanide halide with an ether in a suitable diluent, then contacting the resulting lanthanide composition with an alkali metal alkyl stabilized against beta-hydride elimination, and depositing the resulting lanthanide product on a particulate support.

Martin, S.J.; McDaniel, M.P.; Martin, C.; Martin, B.K.; Martin, J.L.

1992-04-14

318

Polymeric nitrogen  

Microsoft Academic Search

Ab initio local-density functional total-energy calculations indicate that a polymeric form should be the stable phase of nitrogen above [approximately] 35 GPa, and that such a polyermic phase is likely to be both energetic and metastable at atmospheric pressure. These results also suggest that such a polymeric form of nitrogen may survive metastably at atompsheric pressure as an energetic, high-melting

C. Mailhiot; L. H. Yang; A. K. McMahan

1992-01-01

319

Study on preirradiation grafting of methacrylamide onto natural silk fabrics.  

National Technical Information Service (NTIS)

In order to improve the properties of natural silk fabrics, the mechanism and method of the radiation induced graft copolymerization of monomers onto natural silk fabrics were more studied. Grafting of methacrylamide onto natural silk fabrics by the preir...

Xiang Zhengyu Wan Dairong

1997-01-01

320

Modification of natural rubber by different grafting techniques  

NASA Astrophysics Data System (ADS)

An attempt has been made to graft a hydrophylic monomer of N,N.dimethyl acrylamide (DMAA) onto natural rubber (NR) tube by simultaneous, per-oxidation and preirradiation grafting techniques. It was found that the grafting by simultaneous grafting technique results a maximum 29 wt% degree of grafting and by peroxidation and preirradiation techniques, results the maximum 42 wt% and 13 wt% degree of grafting, respectively. It was concluded that the peroxidation technique is the most appropriate to obtain a high degree of grafting in radiation copolymerization of DMAA onto NR.

Razzak, Mirzan T.; Tabata, Yoneho; Otsuhata, Kazushige

1993-07-01

321

Design of novel sheet-shaped chitosan hydrogel for wound healing: a hybrid biomaterial consisting of both PEG-grafted chitosan and crosslinkable polymeric micelles acting as drug containers.  

PubMed

In this study, we successfully prepared a novel "sheet-shaped" chitosan hydrogel for wound healing consisting of both PEG-g-chitosan and a crosslinkable polymeric micelle. The study's findings clarify that the PEG modification percentage (PMP) of PEG-g-chitosan increased proportionally as the weight ratio of PEG/chitosan increased. Furthermore, the positive second virial coefficient of PEG-g-chitosans from a Debye plot strongly suggests that the PEG modification greatly improved the solubility of the water-insoluble chitosan. Finally, the "sheet-shaped" "flexible" hydrogel formed by mixing solutions containing either PEG-g-chitosan with moderate PMP or polymeric micelles exhibited the highest storage modulus. The sheet itself exhibited an attractive feature insofar as polymeric micelles, which can act as drug containers facilitating the incorporation and the gradual release of drugs, are covalently immobilized in the polymeric network of the hydrogel. The results obtained in the present study show that the hybrid PEG-g-chitosan hydrogel containing crosslinkable polymeric micelles has the potential to address the need for novel functional biomaterials. PMID:23910266

Ito, Tomoki; Yoshida, Chikara; Murakami, Yoshihiko

2013-10-01

322

Highly hydrophilic and low-protein-fouling polypropylene membrane prepared by surface modification with sulfobetaine-based zwitterionic polymer through a combined surface polymerization method  

Microsoft Academic Search

Poly(sulfobetaine methacrylate) [poly(SBMA)], a zwitterionic polymer, was successfully tethered in high density onto polypropylene (PP) membrane surface through a combined method consisting of UV-induced surface graft polymerization followed by surface-initiated atom transfer radical polymerization (ATRP). 2-Hydroxyethyl methacrylate (HEMA) was first immobilized onto PP membrane surface by UV-induced graft polymerization, and then each of the grafted poly(HEMA) chains, after coupled with

Yong-Hong Zhao; Kin-Ho Wee; Renbi Bai

2010-01-01

323

Surface Modification of PET Fabric by Graft Copolymerization with Acrylic Acid and Its Antibacterial Properties  

PubMed Central

Graft copolymerization of acrylic acid (AA) onto Poly(ethylene terephthalate) (PET) fabrics with the aid of benzoyl peroxide was carried out. The effect of polymerization parameters on the graft yield was studied. Percent grafting was enhanced significantly by increasing benzoyl peroxide (BP) concentrations up to 3.84?g/lit and then decreased upon further increase in initiator concentration. Preswelling of PET leads to changes in its sorption-diffusion properties and favors an increase in the degree of grafting. The antibiotics treated grafted fabrics showed antibacterial properties towards gram-positive and gram-negative microorganisms. FTIR and SEM were used to characterize AA-grafted polyester fabrics.

Abdolahifard, M.; Bahrami, S. Hajir; Malek, R. M. A.

2011-01-01

324

Location and size of nanoscale free-volume holes in crosslinked- polytetrafluoroethylene-based graft-type polymer electrolyte membranes determined by positron annihilation lifetime spectroscopy  

NASA Astrophysics Data System (ADS)

The location and size of nanoscale free-volume holes (nanoholes) in graft-type polymer electrolyte membranes (PEMs), which were prepared by radiation-induced graft polymerization (grafting) of styrene into crosslinked-polytetrafluoroethylene (cPTFE) films and subsequent sulfonation, were investigated using positron annihilation lifetime (PAL) spectroscopy. The PAL spectra of the PEMs indicated the existence of two types of ortho-positronium (o-Ps) species, corresponding to nanoholes with volumes of 0.11 and 0.38 nm3. A comparison of the PAL data of the PEMs with that of the precursor original cPTFE and polystyrene-grafted films demonstrated the probability that the smaller holes were located in both the PTFE crystalline phases and the poly(styrene sulfonic acid) graft regions, whereas the larger holes are potentially localized in the PTFE amorphous phases. Taking into account both the size and the location of the nanoholes, it was concluded that gas transport through the larger holes in the amorphous PTFE phases was dominant over permeation through the smaller holes in the PTFE crystals and grafted regions.

Sawada, Shin-ichi; Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo; Maekawa, Yasunari

2013-06-01

325

Viability of porcine nasal septal cartilage grafts following Nd:YAG (n=1.32um) laser radiation  

NASA Astrophysics Data System (ADS)

Mechanically deformed morphologic cartilage grafts undergo a temperature dependent phase transformation during sustained laser irradiation that results in reshaping of the specimen. While thermal, optical, and mechanical properties of cartilage undergoing laser heating have been previously investigated, the viability of these irradiated grafts has yet to be examined closely until now. In this study, chondrocyte viability following laser irradiation was determined by measuring the incorporation of radiolabelled sulfate (Na 35SO4-2) into proteoglycan (PTG) macromolecules. Proteoglycans are highly sulfated and are the principal molecular constituents of cartilage matrix. Their synthesis directly reflects chondrocyte viability. By measuring the scintillation counts of 35SO4-2 uptake and normalizing the value by the total protein content of each specimen we can determine the level of PTG synthesis rates following laser reshaping. Regional baseline PTG synthesis rates as a function of location was determined by dividing each specimen into six regions. All regions except the most cephalic are demonstrated similar PTG synthesis rates. The most cephalic region exhibited a significantly greater PTG synthesis rates. In order to establish a positive control for this study, specimens were immersed in boiling saline water for approximately 40 minutes. The boiled specimens demonstrated a fivefold increase in normalized radioisotope uptake and suggest that the non-specific uptake of radioactive Na35SO4-2 is caused by structural alterations in the collagen matrix caused by extensive thermal exposure. To avoid this thermal artifact, another positive control was established using nitric oxide was to induce apoptosis of the chondrocytes, resulting in significantly lower PTG synthesis compared to untreated tissue. Cartilage specimens (25 X 10 X 2 mm) were irradiated with light emitted from an Nd:YAG laser (25 W/cm2, (lambda) equals 1.32 micrometer) while radiometric surface temperature, internal stress, and backscattered light were simultaneously recorded. Individual specimens underwent either one, two, or three sequential laser exposures with the duration of each exposure determined in real-time from observation of characteristic changes in integrated backscattered light intensity that correlate with thermal mediated stress relaxation. A five-minute time interval between each irradiation was given to allow the cartilage to return to thermal equilibrium. Average laser exposure for each irradiation sequence was recorded (5, 8.3, 12.2 sec). PTG synthesis decreased with increasing laser exposure, but was noted to remain above baseline levels for NO treated tissue. To further refine these results and minimize the effect of regional tissue variations, 7 mm diameter discs excised from the most cephalic portions and a middle region of the pig nasal septal cartilages were irradiated. A reduction of PTG synthesis rates was noted with each successive irradiation, suggesting that laser mediated cartilage reshaping acutely does not eliminate the population of viable chondrocytes. The degree of reduction in PTG synthesis is dependent upon the time-temperature dependent heating profile created during laser irradiation, and carefully monitored dosimetry is necessary to ensure chondrocyte viability.

Chao, Kenneth K.; Wong, Brian J.; Kim, Hong K.; Milner, Thomas E.; Sung, Chung-Ho; Sobol, Emil N.; Nelson, J. Stuart

2000-06-01

326

An empirical study into the effect of long term storage (?36±2 °C) of electron-beamed ETFE on the properties of radiation-grafted alkaline anion-exchange membranes  

NASA Astrophysics Data System (ADS)

The application of alkaline anion-exchange membranes (AAEM) in solid alkaline fuel cells is growing in prominence mainly due to enhanced tolerance to carbon dioxide, compared to alkaline fuel cells containing aqueous electrolytes, and the potential for using non precious metal catalysts. Radiation grafting is a common methodology for the production of functional polymers and membranes. This statistical study examines the synthesis of radiation grafted AAEMs that are formed from electron beam irradiated poly(ethylene-co-tetrafluoroethylene), EB-ETFE. It is shown that EB-ETFE can be cold stored for at least 16 months and still be used to produce ionically conductive AAEMs. The limitations of routine measurements of properties, such as dimensional increases, ion-exchange capacity, water uptakes and ionic conductivities, are also highlighted.

Kizewski, Jamie Peter; Mudri, Nurul H.; Varcoe, John R.

2013-08-01

327

Graft copolymerization of acrylonitrile onto bagasse and wood pulps  

SciTech Connect

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50/sup 0/C than at 30/sup 0/C or at 40/sup 0/C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.

Heikal, S.O.; El-Kalyoubi, S.F.

1982-08-01

328

Psyllium and acrylic acid based polymeric networks synthesized under the influence of ? -radiations for sustained release of fungicide  

Microsoft Academic Search

The present study deals with the utilization of psyllium and acrylic acid based hydrogels, synthesized under the influence\\u000a of ?-radiations, in sustained delivery of copper sulfate, used as a fungicide in agricultural fields. Swelling behavior of the\\u000a synthesized hydrogel was investigated in distilled water as functions of time, temperature, and pH. It was found that the\\u000a hydrogel showed maximum of

Kiran Kumar; B. S. Kaith

2010-01-01

329

Induction of NKG2D ligands by gamma radiation and tumor necrosis factor-alpha may participate in the tissue damage during acute graft-versus-host disease.  

PubMed

Immunopathology of acute graft-versus-host disease (aGVHD) involves secretion of proinflammatory cytokines with subsequent expression of danger signals by injured host tissues. This explanation, however, does not explain the cluster of aGVHD target organs (skin, gut, and liver). NKG2D ligands (MICA/B and ULBP1-3 proteins) are stress-induced molecules that act as danger signals to alert NK and alphabeta or gammadelta CD8 T cells through engagement of the activating NKG2D receptor. We observed a strong and reversible induction of MICA/B expression in skin and liver sections during aGVHD. Tumor necrosis factor-alpha and gamma-radiation up-regulated expression of MICA/B and ULBP proteins in vitro on skin and intestine epithelial cell lines and ex vivo in normal skin explants. This NKG2D-ligand induction was regulated by a complex interplay between NFkB and JNK activation pathways. Our data suggest that NKG2D ligand induction might participate in the amplification loop that leads to tissue damage during aGVHD. PMID:18360276

Gannagé, Monique; Buzyn, Agnès; Bogiatzi, Sofia I; Lambert, Marion; Soumelis, Vassili; Dal Cortivo, Liliane; Cavazzana-Calvo, Marina; Brousse, Nicole; Caillat-Zucman, Sophie

2008-03-27

330

Chronic graft-versus-host disease in the rat radiation chimera: I. clinical features, hematology, histology, and immunopathology in long-term chimeras  

SciTech Connect

The clinical features, pathology, and immunopathology of chronic graft-versus-host disease (GVHD) developing in the long-term rat radiation chimera are described. At 6 to 12 months post-transplant, the previously stable ACI/LEW chimeras developed patchy to diffuse severe hair loss and thickened skin folds, and had microscopic features resembling scleroderma, Sjogren's syndrome, and chronic hepatitis. Skin histology showed dermal inflammation and acanthosis with atrophy of the appendages, with progression to dermal sclerosis. The liver revealed chronic hepatitis with bile duct injury and proliferation and periportal piecemeal necrosis. The tongue had considerable submucosal inflammation, muscular necrosis, and atrophy and arteritis. The serous salivary glands, lacrimal glands, and bronchi had lymphocytic inflammation and injury to duct, acinar, and mucosal columnar epithelium. The thymus had lymphocyte depletion of the medulla with prominent epithelium. The spleen and lymph nodes had poorly developed germinal centers but increased numbers of plasma cells. IgM was observed along the basement membrane and around the basal cells of the skin and tongue and along the basement membrane of the bile ducts. IgM was present also in the arteries of the tongue. Immunoglobulins eluted from the skin, cross-reacted with the bile duct epithelium and usually with both ACI and Lewis skin. Increased titers of speckled antinuclear antibodies were present in the serum of rats with chronic (GVHD). Chronic GVHD in the long-term rat radiation chimera is very similar to human chronic GVHD and is a potentially excellent model for autoimmune disorders including scleroderma, Sjorgren's syndrome, and chronic hepatitis.

Beschorner, W.E.; Tutschka, P.J.; Santos, G.W.

1982-04-01

331

Skin graft - series (image)  

MedlinePLUS

... barrier. Skin grafts may be recommended for: extensive wounds burns specific surgeries that may require skin grafts for healing to occur. The most common sites of harvest for skin grafts are the buttocks ...

332

Bone Graft Alternatives  

MedlinePLUS

... or during a surgical procedure such as spinal fusion. What Types of Bone Grafts are There? Bone ... bone grafts in spine surgery is during spinal fusion. The use of autogenous bone grafts for spinal ...

333

Modulation of graft architectures for enhancing hydrophobic interaction of biomolecules with thermoresponsive polymer-grafted surfaces.  

PubMed

This paper describes the effects of graft architecture of poly(N-isopropylacrylamide) (PIPAAm) brush surfaces on thermoresponsive aqueous wettability changes and the temperature-dependent hydrophobic interaction of steroids in silica capillaries (I.D.: 50 ?m). PIPAAm brushes were grafted onto glass substrates by surface-initiated atom transfer radical polymerization (ATRP) that is one of the living radical polymerization techniques. Increases in the graft density and chain length of PIPAAm brushes increased the hydration of polymer brushes, resulting in the increased hydrophilic properties of the surface below the transition temperature of PIPAAm at 32 °C. More hydrophobic surface properties were also observed on surfaces modified with the block copolymers of IPAAm and n-butyl methacrylate (BMA) than that with IPAAm homopolymer-grafted surfaces over the transition temperature. Using PBMA-b-PIPAAm-grafted silica capillaries, the baseline separation of steroids was successfully achieved by only changing temperature. The incorporation of hydrophobic PBMA chains in grafted PIPAAm enhanced the hydrophobic interaction with testosterone above the transition temperature. The surface modification of hydrophobicity-enhanced thermoresponsive polymers is a promising method for the preparation of thermoresponsive biointerfaces that can effectively modulated their biomolecule and cell adsorption with the wide dynamic range of hydrophilic/hydrophobic property change across the transition temperature. PMID:22143027

Idota, Naokazu; Kikuchi, Akihiko; Kobayashi, Jun; Sakai, Kiyotaka; Okano, Teruo

2012-11-01

334

ATRP grafting from cellulose fibers to create block-copolymer grafts.  

PubMed

Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in an earlier work. The papers were analyzed by gravimetry, FT-IR, ESCA, and AFM. To verify that the polymerization from the surface was "living", a second layer of another, hydrophilic, polymer, 2-hydroxyethyl methacrylate (HEMA), was grafted upon the PMA layer, creating a block-copolymer graft from the fibers. After the layer of PHEMA had been attached, contact angle measurements were no longer possible, because of the absorbing nature of PHEMA-grafted layer. This indicates that a copolymer had indeed been formed on the surface. FT-IR showed a large increase in carbonyl content after the PHEMA-grafting, which further proves that a layer of PHEMA was attached to the PMA layer. This goes to show that the hydrophilic/hydrophobic behavior of a cellulose surface can be tailored by the use of "living"/controlled radical polymerization methods such as ATRP. PMID:14606904

Carlmark, Anna; Malmström, Eva E

2003-01-01

335

Hemoglobin loaded polymeric nanoparticles: preparation and characterizations.  

PubMed

In the present work polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with m-PEG (2000) and 95% grafted with 2-methoxyethanol (VAM41-PEG) were loaded with human hemoglobin (Hb) and characterized from a physicochemical point of view. The assessment of structural and functional features of the loaded Hb was performed and the effect of the introduction of different reducing agents as aimed at minimizing Hb oxidation during the nanoparticles formulation process, was also investigated. Nanoparticles possessing an average diameter of 138±10 nm and physicochemical features suitable for this kind of application were successfully obtained. Although the oxidation of the protein was not avoided during its loading into nanoparticles, the presence of acidic moieties in the polymeric structure is proposed to be directly involved in the protein inactivation mechanism. PMID:21443949

Dessy, Alberto; Piras, Anna M; Schirò, Giorgio; Levantino, Matteo; Cupane, Antonio; Chiellini, Federica

2011-05-18

336

Preparation of acrylic grafted chitin for wound dressing application  

Microsoft Academic Search

Chitin grafted with poly(acrylic acid) (chitin–PAA) was prepared with the aim of obtaining a hydrogel characteristic for wound dressing application. The chitin–PAA films were synthesized at various acrylic acid feed contents to investigate its effect on water sorption ability. Acrylic acid (AA) was first linked to chitin, acting as the active grafting sites on the chain that was further polymerized

Siriporn Tanodekaew; Malinee Prasitsilp; Somporn Swasdison; Boonlom Thavornyutikarn; Thanawit Pothsree; Rujiporn Pateepasen

2004-01-01

337

Development of ceramic-supported polymeric membranes for filtration of oil emulsions  

Microsoft Academic Search

Hybrid ceramic-polymeric membranes have been constructed by growing of covalently-bondedpolyvinylpyrrolidone(PVP) chains from the surface of porous inorganic supports via a graft polymerization process. The ability to manipulate the distribution of grafted polymer on the surface has been achieved through the control of the surface density of chain anchoring sites (vinyl silane molecules). The application of the modification procedure to both

Robert P. Castro

1997-01-01

338

Thermal properties and morphology of cassava starch grafted with different content of polystyrene  

Microsoft Academic Search

The interest in replacing synthetic polymers by biodegradable materials from renewable resources is steadily increasing. In\\u000a this work, cassava starch grafted with different content of polystyrene (PS) was synthesized via free-radical polymerization\\u000a using suspension polymerization technique. Thermal data of pure starch and the grafted starch with different content of PS\\u000a were collected by simultaneous thermogravimetric (TG)–differential scanning calorimetry (DSC) setup

Kaewta Kaewtatip; Varaporn Tanrattanakul; Katalin Mészáros Szécsényi; Jelena Pavli?evi?; Jaroslava Budinski-Simendi?

2010-01-01

339

Microfiltration membranes prepared from acryl amide grafted poly(vinylidene fluoride) powder and their pH sensitive behaviour  

Microsoft Academic Search

Acryl amide (AAm) was grafted onto poly(vinylidene fluoride) (PVDF) powder by a pre-irradiation induced graft polymerization technique. The chemical structure of AAm grafted PVDF powder (denoted as PVDF-g-PAM powder) was characterized by FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. Then, the microfiltration (MF) membranes were cast from PVDF-g-PAM powder with different degrees of grafting (DG) using a phase inversion

Xuanxuan Yang; Bo Deng; Zhongying Liu; Liuqing Shi; Xiaokai Bian; Ming Yu; Linfan Li; Jingye Li; Xiaofeng Lu

2010-01-01

340

Preparation and characterization of chemically stable polymer electrolyte membranes by radiation-induced graft copolymerization of four monomers into ETFE films  

Microsoft Academic Search

To develop a highly chemically stable polymer electrolyte membrane for application in a direct methanol fuel cell (DMFC), four styrene derivative monomers, m,p-methylstyrene (MeSt), p-tert-butylstyrene (tBuSt), divinylbenzene (DVB) and bis(p,p-vinyl phenyl) ethane (BVPE) were graft copolymerized into poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by sulfonation and hydrolysis. The latter two monomers were used as crosslinkers. The graft copolymerization was carried out by

Jinhua Chen; Masaharu Asano; Tetsuya Yamaki; Masaru Yoshida

2006-01-01

341

Preparation of functionalized polystyrene latexes by radiation-induced miniemulsion polymerization using a Y-type polymerizable surfactant as sole stabilizers  

NASA Astrophysics Data System (ADS)

Functionalized polystyrene latexes were prepared by miniemulsion polymerization using a Y-type polymerizable surfactant bearing a carboxylic acid group as sole stabilizers. Kinetics analysis showed that there was no constant rate stage, which coincided with the kinetics mechanism of the typical miniemulsion polymerization. The latexes obtained were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the latexes prepared by miniemulsion polymerization initiated by gamma-ray had more narrowly particle size distribution compared with by potassium persulfate. XPS and FTIR results indicated that the carboxyl group was present on the surface of the polymer particles.

Chen, Jun; Zhang, Zhicheng; Zhang, Qianfeng

2009-11-01

342

Starch Graft Polymer Latexes.  

National Technical Information Service (NTIS)

This patent application pertains to starch graft polymer latexes as well as processes for their preparations. The starch graft latexes are water-dispersed grafted starch particles (300-1500 A in size) consisting of either (1) a cationic starch graft polym...

L. A. Gugliemelli C. L. Swanson C. R. Russell

1975-01-01

343

Studies in reactive extrusion processing of biodegradable polymeric materials  

Microsoft Academic Search

Various reaction chemistries such as Polymerization, Polymer cross-linking and Reactive grafting were investigated in twin-screw extruders. Poly (1,4-dioxan-2-one) (PPDX) was manufactured in melt by the continuous polymerization of 1,4-dioxan-2-one (PDX) monomer in a twin-screw extruder using Aluminum tri-sec butoxide (ATSB) initiator. Good and accurate control over molecular weight was obtained by controlling the ratio of monomer to initiator. A screw

Sunder Balakrishnan

2006-01-01

344

Preparation of waterborne polyurethane nanocomposites: Polymerization from functionalized hydroxyapatite  

Microsoft Academic Search

We report the preparation and characterization of waterborne polyurethane (WBPU)\\/hydroxyapatite (HAp) nanocomposites through in situ polymerization from functionalized HAp. The HAp nanoparticles (HAp NPs) were urethanated with 3-isocyanatemethyl-3,5,5-trimethyl-cyclohexylisocyanate (isophorone diisocyanate) to obtain grafted HAp NPs containing isocyanate groups (HAp-g-NCO) as crosslinkers and then the HAp-g-NCO is further polymerized with WBPU monomers to form the WBPU\\/HAp nanocomposites. The HAp NPs were

Cai-Xia Zhao; Wei-De Zhang

2008-01-01

345

Preparation and decoloration property of polystyrene-grafted palygorskite nanoparticles  

Microsoft Academic Search

The polymerization of styrene on inorganic palygorskite nanorods was carried out by reverse atom transfer radical polymerization (RATRP) in a completely controlled manner to form structurally well-defined PS-grafted hybrid nanocomposite. Well-defined PS chains were grown from the nanoparticle surfaces to yield individual particles composed of a palygorskite core and a well-defined outer PS layer. It has been found that the

Zi-Qiang Lei; Shou-Xin Wen

2007-01-01

346

Graft irradiation abrogates graft-versus-host disease in combined pancreas-spleen transplantation  

SciTech Connect

A model of combined pancreas-spleen transplantation (PST) was studied in LBN F1 recipients of Lewis grafts in order to evaluate the efficacy of pretransplant graft irradiation in preventing lethal graft-versus-host disease (GVHD). Recipients of unmodified PST uniformly developed severe GVHD and died (MST = 16.7 +/- 3.8 days). Whole body donor irradiation with either 500 or 250 rad prevented lethal GVHD. Similarly, ex vivo graft irradiation with either 1000 or 500 rad also resulted in normal weight gain, graft function, and host survival for the 6-week study period. Conversely, delay of graft irradiation until 3 days after transplantation failed to prevent this complication (MST = 15.8 +/- 3.7 days). Recipients of irradiated grafts displayed glucose tolerance tests that were identical to those in the control group indicating that the doses of radiation employed in these experiments were not deleterious to islet function. Irradiated spleen grafts appeared histologically normal at 6 weeks after transplantation. Cells derived from these grafts failed to stimulate lymph node enlargement in a popliteal lymph node assay for GVHD, suggesting that these spleens may have become repopulated with host cells. These experiments confirm that PST has the potential to cause lethal GVHD and suggest that pretransplant graft irradiation may be used to prevent its occurrence.

Schulak, J.A.; Sharp, W.J.

1986-04-01

347

Cell behaviour on polymer surfaces grafted with non-ionic and ionic monomers.  

PubMed

Following exposure to corona discharge, a polyethylene film was graft polymerized with different water-soluble monomers such as acrylamide (non-ionic), acrylic acid (anionic), 2-acrylamide-2-methyl propane sulphonic acid (anionic), styrene sulphonic acid sodium salt (anionic) and N,N-dimethylaminopropyl acrylamide (cationic). Attachment and proliferation of HeLa S3 cells were studied for grafted surfaces with different zeta potentials and contact angles. The polyethylene surface graft polymerized with styrene sulphonic acid sodium salt exhibited high cell attachment and protein adsorption, whereas the cells did not adhere to the 2-acrylamide-2-methyl propane sulphonic acid graft-polymerized surface, although both surfaces had high negative zeta potentials. Graft polymerization of acrylamide reduced the zeta potential of surface close to zero and rejected the cell attachment. The polyethylene surface became highly cell-adhesive through graft polymerization of the cationic N,N-dimethylaminopropyl acrylamide monomer, but too much grafting killed the attaching cells. Once the cells attached to a surface without being killed, they could proliferate at the same growth rate, whatever their surface zeta potential. PMID:1799655

Kishida, A; Iwata, H; Tamada, Y; Ikada, Y

1991-10-01

348

Polymerization of Methyl Metacrylate in Schizolobium Parahyba (Vell.) Blake (Guapuruvu) and Pinus Strobus VAR. Chiapensis Mart. Wood Through Gamma Radiation and Temperature.  

National Technical Information Service (NTIS)

Guapuruvu (Schizolobium parahyba) wood samples that were impregnated with the methyl metacrylate monomer and polymerized by the use of gamma rays from a (60)Co source at different dose exposure and total dose is analysed. The impregnation process by vacuu...

M. G. Carneiro

1982-01-01

349

Two Photon Polymerization of Ormosils  

NASA Astrophysics Data System (ADS)

In this work, 3D structures of hybrid polymers-ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows fast micro and nano processing of three-dimensional structures with application in medical devices, tissue scaffolds, photonic crystals etc) was used for monomers processing. As laser a Ti: Sapphire laser was used, with 200 fs pulse duration and 2 kHz repetition rate, emitting at 775 nm. A parametric study on the influence of the processing parameters (laser fluence, laser scanning velocity, photo initiator) on the written structures was carried out. The as prepared polymeric scaffolds were tested in mesenchymal stem cells and fibroblasts cell cultures, with the aim of further obtaining bone and dermal grafts. Cells morphology, proliferation, adhesion and alignment were analyzed for different experimental conditions.

Matei, A.; Zamfirescu, M.; Jipa, F.; Luculescu, C.; Dinescu, M.; Buruiana, E. C.; Buruiana, T.; Sima, L. E.; Petrescu, S. M.

2010-10-01

350

Graft copolymers from unsaturated monomers and azo di-ester polyols and polyurethanes prepared therefrom  

US Patent & Trademark Office Database

Graft copolymers are prepared by the polymerization of an ethylenically unsaturated monomer, or a mixture of such monomers, in the presence of an azo di-ester polyol. Presence of the azo group in the polyol reactant itself serves as a free radical initiator site for the graft copolymerization reaction. The copolymers formed are utilized in the formulation of polyurethane compositions.

1982-11-16

351

Surface modification of cardo polyetherketone ultrafiltration membrane by photo-grafted copolymers to obtain nanofiltration membranes  

Microsoft Academic Search

Hydrophilic nanofiltration membranes were prepared by grafting hydrophilic copolymers onto surface of ultrafiltration membranes. The method consists of a UV irradiation followed by an in situ graft co-polymerization of water soluble monomers on the membranes made of cardo polyetherketone (PEK-C). The effect of irradiation time and monomer nature on the membrane performance was investigated. Analysis by Fourier transform infrared in

Changquan Qiu; Quang Trong Nguyen; Zhenghua Ping

2007-01-01

352

Grafting of a LLDPE using gamma irradiation  

NASA Astrophysics Data System (ADS)

In this investigation, the grafting of a commercial linear low-density polyethylene (LLDPE) with different concentrations of diethyl maleate (DEM, 5 and 15 wt.%) was carried out at different absorbed doses from a cobalt-60 source of gamma rays (0, 15, 30, 50, 100, 200 kGy). This process was performed in a decalin solution at 10% w/v to obtain a homogeneous dispersion of the monomer into the polyethylene matrix. The grafting degree was estimated by means of FTIR using a calibration curve reported in literature. Thermal properties of the functional polymers were studied by thermogravimetric analysis (TGA). Melt flow index (MFI) values were also taken. The results found indicate that the grafting degree increases as the concentration of DEM in the reaction mixture and the absorbed doses are increased upto 100 kGy, as expected. However, the behavior at higher doses is attributed to secondary reactions such as long-chain branching and/or crosslinking, which are faster than radical reactions responsible for the grafting of the DEM onto the polymeric chain. This fact was ascertained by the decrease of the MFI values as the applied irradiation was increased, irrespective of the quantity of DEM used in the grafting reaction. Therefore, in order to obtain a high grafting degree, the absorbed dose should be estimated carefully. Initial degradation temperatures of the grafted PEs decreased when the gamma irradiation dose was higher than 100 kGy. This indicates that the thermal stability decreases as higher doses are applied to the material, which is associated to branching and crosslinking. The grafting degree never exceeded 0.3 mol%, which demonstrates the low efficiency of the functionalization procedure here presented.

Catarí, E.; Albano, C.; Karam, A.; Perera, R.; Silva, P.; González, J.

2005-07-01

353

Living anionic polymerization  

Microsoft Academic Search

For about 40 years living anionic polymerization has been the premier technique for the synthesis of model polymers of controlled architecture and narrow molecular weight distribution (MWD). Nowadays, despite the continuing development of new strategies for the synthesis of well-defined polymers and copolymers (e.g. group transfer polymerization, living radical polymerization, etc.), anionic polymerization continues to be the most reliable and

Kunlun Hong; David Uhrig; Jimmy W Mays

1999-01-01

354

Plasma-induced polymerization for enhancing paper hydrophobicity.  

PubMed

Hydrophobic modification of cellulose fibers was conducted via plasma-induced polymerization in an attempt to graft the hydrophobic polymer chains on paper surface, this increasing the hydrophobicity of paper. Two hydrophobic monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA), were grafted on cellulose fibers, induced by atmospheric cold plasma. Various influencing factors associated with the plasma-induced grafting were investigated. Contact-angle measurement, Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to ascertain the occurrence of the grafting and characterized the changes of the cellulose fiber after modification. The results showed that the hydrophobicity of the modified paper sheet was improved significantly after the plasma-induced grafting. The water contact angle on the paper surface reached up to 130°. The morphological differences between modified and unmodified samples were also revealed by SEM observation. The resulting paper is promising as a green-based packaging material. PMID:23218385

Song, Zhaoping; Tang, Jiebin; Li, Junrong; Xiao, Huining

2013-01-30

355

Electrostrictive Graft Elastomers  

NASA Technical Reports Server (NTRS)

An electrostrictive graft elastomer has a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules. The polar graft moieties have been rotated by an applied electric field, e.g., into substantial polar alignment. The rotation is sustained until the electric field is removed. In another embodiment, a process for producing strain in an elastomer includes: (a) providing a graft elastomer having a backbone molecule which is a non-crystallizable, flexible macromolecular chain and a grafted polymer forming polar graft moieties with backbone molecules; and (b) applying an electric field to the graft elastomer to rotate the polar graft moieties, e.g., into substantial polar alignment.

Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor); St.Clair, Terry L. (Inventor)

2003-01-01

356

Molecular engineering of side-chain liquid crystalline polymers by living polymerizations  

Microsoft Academic Search

“Living” anionic, cationic, metalloporphyrin and ring-opening metathesis polymerizations have been used to prepare well-defined side-chain liquid crystalline homopolymers, block and graft copolymers and statistical copolymers. This paper analyzes their successes and failures by reviewing the mechanistic aspects and experimental conditions of each type of polymerization, and identifies other classes of mesogenic monomers that could be polymerized in a controlled manner

Coleen Pugh; Alan L. Kiste

1997-01-01

357

Polymerization of perfluorobutadiene at near-ambient conditions  

NASA Technical Reports Server (NTRS)

Peroxide catalyst under mild conditions initiates homopolymerization of perfluoro butadiene to new linear perfluoro polyenes and vulcanizable fluoro elastomers. Resulting polyperfluoro butadiene serves as hard elastomer for good chemical resistance, as intermediate in graft polymerizations, and as crosslink for high molecular weight materials.

Toy, M. S.

1971-01-01

358

Surface relief polymer structures grafted onto polymer films  

Microsoft Academic Search

Graft polymerization of glycidyl methacrylate was used to produce surface relief structures on polymer substrates that were exposed with EUV light in a gray-scale exposure. In contrast to conventional lithography, which is in general tuned to be a binary process with a sharp discrimination of exposed and non-exposed areas, different exposure doses are directly transferred into a height profile in

Celestino Padeste; Patrick Farquet; Harun H. Solak

2006-01-01

359

Polymer Grafted Janus Multi-Walled Carbon Nanotubes  

SciTech Connect

We describe a novel and facile strategy to modify the surface of carbon nanotubes (CNTs) with two chemically different polymer brushes utilizing the grafting from technique. A [4 + 2] Diels Alder cycloaddition reaction was used to functionalize multi-walled carbon nanotubes (MWNTs) with two different precursor initiators, one for ring opening polymerization (ROP) and one for atom transfer radical polymerization (ATRP). The binary functionalized MWNTs were used for the simultaneous surface initiated polymerizations of different monomers resulting in polymer grafted MWNTs that can form Janus type structures under appropriate conditions. 1H NMR, FTIR and Raman spectra showed that the precursor initiators were successfully synthesized and covalently attached on the CNT surface. Thermogravimetric analysis (TGA) revealed that the grafted polymer content varies when different monomer ratios and polymerization times are used. The presence of an organic layer around the CNTs was observed through transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) proved that the glass transition (Tg) and melting (Tm) temperatures of the grafted polymers are affected by the presence of the CNTs, while circular dichroism (CD) spectra indicated that the PLLA ahelix conformation remains intact.

Priftis, Dimitrios [ORNL; Sakellariou, Georgios [ORNL; Baskaran, Durairaj [University of Tennessee, Knoxville (UTK); Mays, Jimmy [ORNL; Hadjichristidis, Nikos [University of Athens, Athens, Greece

2009-01-01

360

Gamma-radiation-induced grafting of binary mixture of methacrylic acid and 4-vinyl pyridine onto Teflon-FEP film as an effective polar membrane for separation processes  

NASA Astrophysics Data System (ADS)

Ionic bifunctional membranes have been synthesized by grafting binary mixture of methacrylic acid (MAAc) and 4-vinyl pyridine (4-VP) onto Teflon-FEP film by pre-irradiation method. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of binary mixture (MAAc-co-4-VP) (71.29%) was obtained at an optimum total dose of 54.48 kGy and the total concentration was 9.49 mol/L ([4-VP] = 0.07 mol/L and [MAAc ] = 9.42 mol/L) in 5 ml of water. The effect of alcohols as additives to the reaction medium on percent grafting of the binary mixture has also been studied. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. Swelling studies of the membranes were performed in different solvents such as water, benzene, carbon tetrachloride and dimethyl formamide (DMF). Maximum swelling was observed in DMF with minimum swelling in benzene. Metal ion (Cu 2+, Ni 2+ and Fe 2+) uptake studies show better affinity for Fe 2+ ions. Conductance measurements in different aqueous salt solution showed that these membranes have affinity for Na +/K + ions and Cl - ions and hence can be used in desalination/separation processes for the separation of both type of cationic and anionic ions.

Kaur, Inderjeet; Rattan, Sunita; Chauhan, Sandeep; Gupta, Nitika

2010-05-01

361

Free and microvascular bone grafting in the irradiated dog mandible  

SciTech Connect

Microvascular and free rib grafts were placed in 4.5 cm defects in an edentate mandibular body defect 18 to 28 days after completion of 50 Gy of irradiation from a /sup 60/Co source. The animals were sacrificed from two to forty weeks postoperatively and evaluated clinically, radiographically, and histologically. There was a marked difference in the alveolar mucosal viability with the two grafts. Mucosal dehiscence was not observed over any of the microvascular grafts, but was present in seven-eighths of the free grafts. Union of the microvascular bone graft to the host bone occurred within six weeks. In contrast, after six weeks the free graft was sequestered in all the animals. An unexpected finding with both types of graft was the marked subperiosteal bone formation. This bone appeared to be derived from the host bed, stabilizing and bridging the defects bilaterally. The results suggest that radiated periosteum may play an important role in osteogenesis.

Altobelli, D.E.; Lorente, C.A.; Handren, J.H. Jr.; Young, J.; Donoff, R.B.; May, J.W. Jr.

1987-01-01

362

Skin graft (image)  

MedlinePLUS

... stretch it into a larger patch. If the defect involves a great loss of tissue, a full thickness graft, a flap of skin with underlying muscle and blood vessels, may be required. Taking the graft from the ...

363

Bone grafts in dentistry  

PubMed Central

Bone grafts are used as a filler and scaffold to facilitate bone formation and promote wound healing. These grafts are bioresorbable and have no antigen-antibody reaction. These bone grafts act as a mineral reservoir which induces new bone formation.

Kumar, Prasanna; Vinitha, Belliappa; Fathima, Ghousia

2013-01-01

364

Poly(amide-graft-acrylate) interfacial compounds  

NASA Astrophysics Data System (ADS)

Graft copolymers with segments of dissimilar chemistries have been shown to be useful in a variety of applications as surfactants, compatibilizers, impact modifiers, and surface modifiers. The most common route to well defined graft copolymers is through the use of macromonomers, polymers containing a reactive functionality and thus capable of further polymerization. However, the majority of the studies thus far have focused on the synthesis of macromonomers capable of reacting with vinyl monomers to form graft copolymers. This study focused on the synthesis of macromonomers capable of participating in condensation polymerizations. A chain transfer functionalization method was utilized. Cysteine was evaluated as a chain transfer agent for the synthesis of amino acid functionalized poly(acrylate) and poly(methacrylate) macromonomers. Low molar mass, functionalized macromonomers were produced. These macromonomers were proven to be capable of reacting with amide precursors to form poly(amide-g-acrylate) graft copolymers. Macromonomers and graft copolymers were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, elemental analysis (EA), inductively coupled plasma (ICP), and differential scanning calorimetry (DSC). The second part of this research involved poly(dimethacrylate) dental restorative materials. Volumetric shrinkage during the cure of these resins results in a poor interface between the resin and the remaining tooth structure, limiting the lifetime of these materials. Cyclic anhydrides were incorporated into common monomer compositions used in dental applications. Volume expansion from the ring opening hydrolysis of these anhydrides was shown to be feasible. The modified dental resins were characterized by swelling, extraction and ultraviolet spectroscopy (UV), and density measurements. Linear poLymers designed to model the crosslinked dental resins were characterized by FTIR, GPC, and DSC.

Zamora, Michael Perez

365

Polymeric Materials for Tissue Engineering of Arterial Substitutes  

PubMed Central

Cardiovascular disease is the leading cause of mortality in the United States. The limited availability of healthy autologous vessels for bypass grafting procedures has led to the fabrication of prosthetic vascular conduits. Synthetic polymeric materials, while providing the appropriate mechanical strength, lack the compliance and biocompatibility that bioresorbable and naturally occurring protein polymers offer. Vascular tissue engineering approaches have emerged in order to meet the challenges of designing a vascular graft with long-term patency. In vitro culture techniques that have been explored with vascular cell seeding of polymeric scaffolds and the use of bioactive polymers for in situ arterial regeneration have yielded promising results. This review describes the development of polymeric materials in various tissue engineering strategies for the improvement in the mechanical and biological performance of an arterial substitute.

Ravi, Swathi; Qu, Zheng; Chaikof, Elliot L.

2009-01-01

366

Temperature-Sensitive Polypropylene Membranes Prepared by Plasma Polymerization  

SciTech Connect

PolyN-isopropylacylamide (PNIPAAm) was grafted on polypropylene (PP) microfiltration membranes using plasma polymerization. The surface of the grafted membrane was evaluated by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy pictures demonstrated that the PNIPAAm can be grafted either on the surface or in the pores of the membrane. The morphology of the grafted membrane can be adjusted through monomer concentration and polymerization time. Surface properties with a reversible response to temperature change were observed by measuring the dynamic contact angle. Below the LCST of PNIPAAm, the grafted PP membrane exhibited a hydrophilic surface (advancing contact angle < 40?). Above the LCST, the surface changed to hydrophobic properties (advancing contact angle > 90?). We investigated the on-off characteristics of the grafted membrane by measuring water flux through the grafted membrane at different temperatures. The water flux can be varied from 25 to 7 500 kg/m2 per hr, depending on the temperature and pressure drop. The swelling PNIPAAm chains block the pores of the microfiltration membrane, and the flux decreases (off status). The PNIPAAm chains shrink above the LCST and open the pores of the microfiltration membrane. Thus the water flux increases (on status). The effect of pressure drop on the water flux of the grafted PP membrane was discussed. The rapid and remarkable changes in the pore size of the membrane may make it possible to use the grafted PP membranes as the carrier for a drug-delivery system. They would also be used as multifunctional separation membranes, control valves, and actuators.

Liang, Liang; Shi, Ming-Kun; Viswanathan, Vilayanur V.; Peurrung, Loni M.; Young, James S.

2000-08-30

367

Grafting of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole onto polymers with aliphatic groups. Synthesis and polymerization of 2 (2-hydroxy-5-isopropenylphenyl) 2H-benzotriazole and a new synthesis of 2 (2-hydroxy-5-vinylphenyl) 2H-benzotriazole  

NASA Technical Reports Server (NTRS)

Successful grafting of 2(2-hydroxy-5-vinylphenyl)2H-benzotriazole onto saturated aliphatic C-H groups of polymers has been accomplished. When the grafting reaction was carried out in chlorobenzene at 150 C = 160 C with di-tertiarybutylperoxide as the grafting initiator, grafts as high as 20 percent - 30 percent at a grafting efficiency of 50 percent and 80 percent have readily been obtained. The grafting reaction was carried out in tubes sealed under high vacuum since trace amounts of oxygen cause complete inhibition of the grafting reaction by the phenolic monomer. On a variety of different polymers including atactic polypropylene, ethylene/vinyl acetate copolymer, poly(methyl methacrylate), poly(butyl acrylate), and polycarbonate were used.

Pradellok, W.; Nir, Z.; Vogl, O.

1981-01-01

368

Polymeric Applications in Electronics  

NASA Technical Reports Server (NTRS)

Training manual shows how to use polymeric materials in fabrication electronic components. Report discusses polymeric applications in fabrication of electronic components and equipment. Intended as training manual for 6-day quality assurance and technician certification course in use of polymeric materials.

Read, W. S.

1983-01-01

369

[The St. Jude biopolymeric graft in reconstruction of peripheral arteries].  

PubMed

The authors present their preliminary results of St. Jude Bio Polymeric graft application in the periphery arteries reconstruction. This biograft like all the previous ones (Soleo, CB.S., human umbilical veins) was introduced with the aim of creating a better substitute for autovenous Graft, which has been irreplacible ever before, especially in cases of crural reconstruction. The operated patients were classified into the II stadium of occlusive disease (claudication) and indications for surgery have been based on Doppler sonography and arteriography. In three cases crural femoro-popliteal reconstruction was carried out, because of an occlusion of the superficial femoral artery, in one case a femoro-femoro cross over bypass due to an occlusion of the iliac artery. Postoperative follow-up ranged from 6 to 12 months and the control of the graft passage by. Doppler sonography and arteriography confirmed patency of all grafts. I.e. the preliminary results are excellent. PMID:8701683

Lotina, S; Davidovi?, L; Cinara, I

1990-01-01

370

Biodegradable nanoparticles made from polylactide-grafted dextran copolymers.  

PubMed

Polysaccharide-covered polyester nanoparticles were prepared using the emulsion/solvent evaporation process. The core of the nanoparticles was made either of PLA or of a blend of polylactide and polylactide-grafted dextran copolymer in various proportions. The surface of the nanoparticles was covered by dextran chains via the use of water-soluble polylactide-grafted dextrans as polymeric stabilizers during the emulsification step. The characteristics of the nanoparticles (size, surface coverage, thickness of superficial layer, colloidal stability) were correlated to the structural parameters (length and number of polylactide grafts) of the copolymers as well as to their surface active properties. The complete biodegradability of the nanoparticles was evaluated by considering the rate of hydrolysis of polylactide grafts in phosphate buffer and the rate of enzymatic degradation of dextran backbone by dextranase. PMID:19022457

Nouvel, C; Raynaud, J; Marie, E; Dellacherie, E; Six, J-L; Durand, A

2009-02-15

371

Studies on surface grafting of AAc\\/SSS binary monomers onto polytetrafluoroethylene by dielectric barrier discharge initiation  

Microsoft Academic Search

Polytetrafluoroethylene (PTFE) films were pre-treated by dielectric barrier discharge in atmospheric pressure with air as carrier gas. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effects of binary monomer ratio, reaction solution concentration and polymerization time on the degree of grafting

Zhen-Yu Xi; You-Yi Xu; Li-Ping Zhu; Fu Liu; Bao-Ku Zhu

2008-01-01

372

Surface-grafted polypeptides on flat substrates  

NASA Astrophysics Data System (ADS)

In this work, we improved the vapor deposition-polymerization (VDP) technique by re-designing a new vacuum chamber, and adding two heating plates to control the temperatures of the substrate and monomer evaporation. By optimizing the reaction parameters such as monomer amount, substrate temperature and reaction time, various polypeptides with sufficiently high molecular weight have been successfully grafted onto the solid substrates. The combination of VPD with photolithography has fabricated micro-patterned polypeptides, with geometry patternable in both lateral and vertical directions. Next, the conformations of the surface-grafted polypeptides were systematically examined. New ways have been found to switch their conformations between alpha-helix and beta-sheet, or between right-handed helix and left-handed helix. Two important ionic polypeptides, poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) were the focuses of this work. The conformational transitions of surface-grafted PLGA and PLL were successfully induced by pH, surfactants and ions. In addition, a surface-grafted PLGA-block-PLL copolypeptide was studied. Their unexpected pH-responsiveness was explained by the beta-sheet formation between the PLGA and PLL blocks. The orientation of the surface-grafted alpha-helical poly(gamma-benzyl L-glutamate) (PBLG) was greatly improved by a novel "solvent quenching" method, which involves treating the film sequentially with a good solvent and a poor solvent. The average tilt angle of the PBLG rods changed from 49° to 3° by applying this "quenching". Finally, a surface-grafted PLL film was used as the template to mimic the biosilicification. Silica was spontaneously synthesized from tetraethoxysilane inside the PLL film at room temperature and at neutral pH.

Wang, Yuli

373

Preparation and characterization of poly(trimethylolpropane triacrylate)\\/flaky aluminum composite particle by in situ polymerization  

Microsoft Academic Search

Poly(trimethylolpropane triacrylate)\\/flaky aluminum composite particle was prepared by in situ polymerization in order to improve the corrosion resistance and adhesive property of aluminum pigments. The effect of monomer concentration, initiator concentration and feeding mode on the conversion, percentage of grafting and grafting efficiency in the preparation was studied. It was found that poly(trimethylolpropane triacrylate) had been successfully grafted on the

Hui Liu; Hongqi Ye; Yingchao Zhang; Xinde Tang

2008-01-01

374

Preparation and surface characterization of functional group-grafted and heparin-immobilized polyurethanes by plasma glow discharge  

Microsoft Academic Search

Functional group-grafted polyurethanes were prepared by oxygen plasma discharge treatment, followed by graft polymerization of 1-acryloylbenzotriazole (AB) and a subsequent substitution reaction of AB with sodium hydroxide and ethylene diamine. The primary amine or carboxylic acid groups grafted on the surfaces were coupled with heparin using water-soluble carbodiimide. The modified surfaces were characterized by measuring the water contact angle, electron

Inn-Kyu Kang; Oh Hyeong Kwon; Young Moo Lee; Yong Kiel Sung

1996-01-01

375

Polymeric Gel Electrolytes for Electrochemical Capacitors  

NASA Astrophysics Data System (ADS)

Three kinds of the polymer matrix, poly(ethylene oxide)-grafted polymethacrylate (PEO-PMA), poly(vinyldene fluoride) (PVdF) and poly(vinyldene-co-hexafluoropripylene) (PVdF-HFP), were used for gel preparation. A proper amount of organic salts or acids were dissolved in the polymer matrix together with organic plasticizers, dimethylformamide (DMF) and/or poly-(efhylene glycol)-dimethylether (PEGDE), without water. Thin films of the polymeric gel were obtained by either direct polymerization of the mixed monomer solution or a thermal casting method. The composition of the polymer-electrolyte complex system is optimized to obtain good capacitor performances of the electrochemical capacitor (ECC) system.

Morita, Masayuki; Qiao, Jin-Li; Ohsumi, Naoki; Yoshimoto, Nobuko; Egashira, Minato

2006-06-01

376

Polymeric material for anti-biofouling.  

PubMed

Copolymerization of methyl methacrylate (MMA) and acrylate terminated poly(ethylene oxide-co-ethylene carbonate) (PEOC) macromonomer yields graft copolymer with PEOC side chains. By use of quartz crystal microbalance with dissipation (QCM-D), we have investigated the adsorption of proteins on the surface constructed by the copolymer in seawater. It shows the polymeric surface exhibits protein resistance depending on the content of the side chains. Marine field tests show the protein resistant surface can effectively inhibit marine biofouling for more than 12 weeks. PMID:22766280

Ma, Chunfeng; Yang, Hongjun; Zhou, Xi; Wu, Bo; Zhang, Guangzhao

2012-12-01

377

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide).  

PubMed

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment. PMID:24681372

Akiyama, Yoshikatsu; Kikuchi, Akihiko; Yamato, Masayuki; Okano, Teruo

2014-08-01

378

Effects of T cell depletion in radiation bone marrow chimeras. III. Characterization of allogeneic bone marrow cell populations that increase allogeneic chimerism independently of graft-vs-host disease in mixed marrow recipients  

SciTech Connect

The opposing problems of graft-vs-host disease vs failure of alloengraftment severely limit the success of allogeneic bone marrow transplantation as a therapeutic modality. We have recently used a murine bone marrow transplantation model involving reconstitution of lethally irradiated mice with mixtures of allogeneic and syngeneic marrow to demonstrate that an allogeneic bone marrow subpopulation, removed by T cell depletion with rabbit anti-mouse brain serum and complement (RAMB/C), is capable of increasing levels of allogeneic chimerism. This effect was observed in an F1 into parent genetic combination lacking the potential for graft-vs-host disease, and radiation protection studies suggested that it was not due to depletion of stem cells by RAMB/C. We have now attempted to characterize the cell population responsible for increasing allogeneic chimerism in this model. The results indicate that neither mature T cells nor NK cells are responsible for this activity. However, an assay involving mixed marrow reconstitution in an Ly-5 congenic strain combination was found to be more sensitive to small degrees of stem cell depletion than radiation protection assays using three-fold titrations of bone marrow cells. Using this assay, we were able to detect some degree of stem cell depletion by treatment with RAMB/C, but not with anti-T cell mAb. Nevertheless, if the effects of alloresistance observed in this model are considered, the degree of stem cell depletion detected by such mixing studies in insufficient to account for the effects of RAMB/C depletion on levels of allogeneic chimerism, suggesting that another cell population with this property remains to be identified.

Sykes, M.; Chester, C.H.; Sundt, T.M.; Romick, M.L.; Hoyles, K.A.; Sachs, D.H. (National Cancer Institute, Bethesda, MD (USA))

1989-12-01

379

Staple viscose rayon modified with graft polystyrene  

Microsoft Academic Search

the necessary processability in the weaving and knitting sectors. The staff of the laboratories of the Moscow Textile Institute have produced several modified viscose rayon staple fibres by grafting with various monomers. One of these is based on a co-polymer of cellulose with polystyrene. The fibre is highly hydrophobic and stable to mineral acids and UV and y radiation \\/2\\/

M. P. Berezeva; E. N. Chernov; B. P. Morin; Z. A. Rogovin

1973-01-01

380

Chitosan-Graft-Branched Polyethylenimine Copolymers: Influence of Degree of Grafting on Transfection Behavior  

PubMed Central

Background Successful non-viral gene delivery currently requires compromises to achieve useful transfection levels while minimizing toxicity. Despite high molecular weight (MW) branched polyethylenimine (bPEI) is considered the gold standard polymeric transfectant, it suffers from high cytotoxicity. Inversely, its low MW counterpart is less toxic and effective in transfection. Moreover, chitosan is a highly biocompatible and biodegradable polymer but characterized by very low transfection efficiency. In this scenario, a straightforward approach widely exploited to develop effective transfectants relies on the synthesis of chitosan-graft-low MW bPEIs (Chi-g-bPEIx) but, despite the vast amount of work that has been done in developing promising polymeric assemblies, the possible influence of the degree of grafting on the overall behavior of copolymers for gene delivery has been largely overlooked. Methodology/Principal Findings With the aim of providing a comprehensive evaluation of the pivotal role of the degree of grafting in modulating the overall transfection effectiveness of copolymeric vectors, we have synthesized seven Chi-g-bPEIx derivatives with a variable amount of bPEI grafts (minimum: 0.6%; maximum: 8.8%). Along the Chi-g-bPEIx series, the higher the degree of grafting, the greater the ?-potential and the cytotoxicity of the resulting polyplexes. Most important, in all cell lines tested the intermediate degree of grafting of 2.7% conferred low cytotoxicity and higher transfection efficiency compared to other Chi-g-bPEIx copolymers. We emphasize that, in transfection experiments carried out in primary articular chondrocytes, Chi-g-bPEI2.7% was as effective as and less cytotoxic than the gold standard 25 kDa bPEI. Conclusions/Significance This work underlines for the first time the pivotal role of the degree of grafting in modulating the overall transfection effectiveness of Chi-g-bPEIx copolymers. Crucially, we have demonstrated that, along the copolymer series, the fine tuning of the degree of grafting directly affected the overall charge of polyplexes and, altogether, had a direct effect on cytotoxicity.

Pezzoli, Daniele; Olimpieri, Francesca; Malloggi, Chiara; Bertini, Sabrina; Volonterio, Alessandro; Candiani, Gabriele

2012-01-01

381

Applications of positron annihilation spectroscopy to polymeric membranes  

Microsoft Academic Search

Positron annihilation spectroscopy (PAS) coupled with a slow positron beam has been used to study the freevolume depth profile (0–10 ?m) in polymeric membrane systems prepared by the interfacial polymerization method. Doppler broadening energy parameters of annihilation radiation vary as a function of the depth from the surface through multi-layers in polyamide asymmetric membranes prepared under different experimental parameters, such

Y. C. Jean; Wei-Song Hung; Chia-Hao Lo; Hongmin Chen; Guang Liu; Lakshmi Chakka; Mei-Ling Cheng; D. Nanda; Kuo-Lun Tung; Shu-Hsien Huang; Kueir-Rarn Lee; Juin-Yih Lai; Yi-Ming Sun; Chien-Chieh Hu; Chang-Cheng Yu

2008-01-01

382

The graft polymers from different species of lignin and acrylic acid: synthesis and mechanism study.  

PubMed

The influence of lignin species on the grafting mechanism of lignosulfonate (from eucalyptus and pine, recorded as HLS and SLS, respectively) with acrylic acid (AA) was investigated. The graft polymers were confirmed by the absorption of carbonyl groups in the FTIR spectra. The decreasing phenolic group's content (Ph-OH) is not only due to its participation as grafting site but also to the negative effect of initiator. In the initial period (0-60 min), HLS and SLS both accelerate the polymerization of AA. Additionally, Ph-OH group's content is proportional to product yield (Y%), monomer conversion (C%) and grafting efficiency (GE%), strongly indicating that it acts as active center. Nevertheless, compared with HLS, Y% and C% in SLS grafting system are lower though it has higher Ph-OH group's content, which is due to the quinonoid structure formed by the self-conjugated of phenoxy radical in Guaiacyl unit. Finally, the lignosulfonate grafting mechanism was proposed. PMID:24076194

Ye, De zhan; Jiang, Li; Ma, Chao; Zhang, Ming-hua; Zhang, Xi

2014-02-01

383

A Versatile Star PEG Grafting Method for the Generation of Nonfouling and Nonthrombogenic Surfaces  

PubMed Central

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15?min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns.

Thalla, Pradeep Kumar; Contreras-Garcia, Angel; Fadlallah, Hicham; Barrette, Jeremie; De Crescenzo, Gregory; Merhi, Yahye; Lerouge, Sophie

2013-01-01

384

Graft copolymers with hydrophilic and hydrophobic polyether side chains  

Microsoft Academic Search

Poly(ethylene glycol)methyl ether methacrylate (PEOMA) and oligo(propylene glycol)-4-nonylphenyl ether acrylate (OPOPhNA) were copolymerized by atom transfer radical polymerization (ATRP). Grafting through method was employed in the presence of CuBr\\/HMTETA or CuBr\\/PMDETA catalyst\\/ligand complex in anisole at 70°C. It yielded a heterografted copolymers containing hydrophilic PEO and hydrophobic OPOPhNA side chains with polymerization degree DP=68–315 in the presence of PMDETA and

Dorota Neugebauer

2007-01-01

385

Graft Polymerization of Vinyl Monomers at Carbon Black Surface (1).  

National Technical Information Service (NTIS)

Effect of aromatic condensates containing functional group on carbon black surface, effect of pH condensates on carbon black chemisorption, analysis and configuration of functional group, the crystal structure, property measurement standard, particle diam...

Haryono Arumbinang

1976-01-01

386

Activation of polymeric materials towards enzymatic postgrafting and cross-linking.  

PubMed

A methodology to activate inert polymeric materials to enzymatic functionalisation is described herein. Plasma irradiation can be used to graft compounds containing a moiety that is reactive towards an enzyme of interest. Subsequently, such enzyme can be used to either postgraft functional compounds or cross-link the polymeric materials. Argon plasma was utilised to graft 2-aminoethyl methacrylate onto cotton and wool fibres, introducing surface alkylamine groups to impart reactivity towards transglutaminase and tyrosinase. The efficiency of plasma grafting was verified by ATR-FTIR. Enzyme postgrafting of fluorescent peptides coupled with confocal microscopy was used to demonstrate transglutaminase activity towards cotton, a material typically inert to this enzyme. The grafting of alkylamines onto wool resulted in additional cross-linking by both enzymes, leading to significantly increased yarn breaking load and elongation at break. This technology permits the activation of inert materials towards enzymatic postgrafting, with applications in fields as diverse as textiles and biomaterials. PMID:22975121

Fatarella, E; Ciabatti, I; Cortez, J

2012-10-10

387

Free radical grafting kinetics of acrylamide onto a blend of starch/chitosan/alginate.  

PubMed

Grafting of monomer onto polymer backbone is one of the effective and accessible methods for the chemical modification of polysaccharides. Grafting of acrylamide (AAm) onto polysaccharides blend (PsB) composed of starch, chitosan and alginate has been carried out using potassium persulfate (KPS) as an initiator. The kinetics of the grafting polymerization also has been studied. The grafting parameters have been evaluated by changing the initial concentrations of AAm from 8 to 16 g, PsB from 6 to 14 g and KPS from 0.2 to 1 g. Evidence of grafting has been obtained from FTIR, XRD and TGA. The kinetics of the grafting polymerization also has been studied. The grafting rate equation of the produced hydrogel (PsB-g-AAm) hydrogel has been expressed by: Rg=k[AAm] [PsB](0.5) [KPS](0.5). The grafting rate is a first order dependence to [AAm] initial concentration and square root to [PsB] and [KPS] initial concentrations in the used concentrations range. PMID:23987368

Sorour, Mohamed; El-Sayed, Marwa; El Moneem, Nabil Abd; Talaat, Hala; Shaalan, Hayam; El Marsafy, Sahar

2013-10-15

388

Toward living radical polymerization.  

PubMed

Radical polymerization is one of the most widely used processes for the commercial production of high-molecular-weight polymers. The main factors responsible for the preeminent position of radical polymerization are the ability to polymerize a wide array of monomers, tolerance of unprotected functionality in monomer and solvent, and compatibility with a variety of reaction conditions. Radical polymerization is simple to implement and inexpensive in relation to competitive technologies. However, conventional radical polymerization severely limits the degree of control that researchers can assert over molecular-weight distribution, copolymer composition, and macromolecular architecture. This Account focuses on nitroxide-mediated polymerization (NMP) and polymerization with reversible addition-fragmentation chain transfer (RAFT), two of the more successful approaches for controlling radical polymerization. These processes illustrate two distinct mechanisms for conferring living characteristics on radical polymerization: reversible deactivation (in NMP) and reversible or degenerate chain transfer (in RAFT). We devised NMP in the early 1980s and have exploited this method extensively for the synthesis of styrenic and acrylic polymers. The technique has undergone significant evolution since that time. New nitroxides have led to faster polymerization rates at lower temperatures. However, NMP is only applicable to a restricted range of monomers. RAFT was also developed at CSIRO and has proven both more robust and more versatile. It is applicable to the majority of monomers subject to radical polymerization, but the success of the polymerization depends upon the selection of the RAFT agent for the monomers and reaction conditions. We and other groups have proposed guidelines for selection, and the polymerization of most monomers can be well-controlled to provide minimal retardation and a high fraction of living chains by using one of just two RAFT agents. For example, a tertiary cyanoalkyl trithiocarbonate is suited to (meth)acrylate, (meth)acrylamide, and styrenic monomers, while a cyanomethyl xanthate or dithiocarbamate works with vinyl monomers, such as vinyl acetate or N-vinylpyrrolidone. With the appropriate choice of reagents and polymerization conditions, these reactions possess most of the attributes of living polymerization. We have used these methods in the synthesis of well-defined homo-, gradient, diblock, triblock, and star polymers and more complex architectures, including microgels and polymer brushes. Applications of these polymers include novel surfactants, dispersants, coatings and adhesives, biomaterials, membranes, drug-delivery media, electroactive materials, and other nanomaterials. PMID:18700787

Moad, Graeme; Rizzardo, Ezio; Thang, San H

2008-09-01

389

Olefin polymerization catalyst and process of polymerization  

SciTech Connect

This patent describes a process of producing a lower [alpha]-olefin polymer. It comprises contacting under polymerization conditions one or more lower [alpha]-olefins with an olefin polymerization catalyst obtained by contacting a catalyst component obtained by contacting a magnesium dialkoxide wherein each alkoxide independently has up to 4 carbon atoms conclusive, titanium tetraalkoxide wherein each alkoxide independently has up to 4 carbon atoms inclusive, and a phenolic compound selected from phenol and activating group-substituted phenol, at elevated temperature, with a tetravalent titanium halide and an electron donor, with an organoaluminum cocatalyst and a selectively control agent.

Job, R.C.

1992-09-08

390

Polypeptoid Brushes by Surface-Initiated Polymerization of N-Substituted Glycine N-Carboxyanhydrides  

PubMed Central

Polypeptoid brushes were synthesized by surface-initiated polymerization of N-substituted glycine N-carboxyanhydrides (NNCAs) on self assembled amine monolayers. Using the presented grafting from approach, polypeptoid brush thicknesses of approx. 40 nm could be obtained as compared previously reported brush thicknesses of 4 nm. Moreover, hydrophilic, hydrophobic and amphiphilic polymer brushes were realized which are expected to have valuable applic-tions as non-fouling surfaces and as model or references systems for surface grafted polypeptides.

Schneider, Maximilian; Fetsch, Corinna; Amin, Ihsan; Jordan, Rainer; Luxenhofer, Robert

2013-01-01

391

Analysis of the Complexation\\/Decomplexation Phenomena in Graft Copolymer Networks  

Microsoft Academic Search

Graft copolymer networks of poly(methacrylic acid-g-ethylene glycol) exhibiting pH- dependent swelling behavior due to the formation of interpolymer complexes were prepared by free radical solution polymerization of methacrylic acid and poly(ethylene glycol) monomethacrylate. Dynamic swelling studies established the swelling\\/deswelling process due to hydrogen bonding. Additionally, the effects of copolymer composition, graft chain molecular weight, and environmental pH on network structure

Anthony M. Lowman; Nikolaos A. Peppas

1997-01-01

392

Complexation graft copolymer networks: swelling properties, calcium binding and proteolytic enzyme inhibition  

Microsoft Academic Search

Graft copolymer networks of poly(methacrylic acid-g-ethylene glycol) were prepared by free radical solution UV-polymerization of methacrylic acid (MAA) and poly(ethylene glycol) monomethacrylate. Dynamic swelling studies indicated that complexation\\/decomplexation processes occurred due to hydrogen bonding between the carboxylic groups of the poly(methacrylic acid) (PMAA) and the ether groups of poly(ethylene glycol) (PEG). The effects of copolymer composition, graft chain molecular weight,

Flemming Madsen; Nikolaos A. Peppas

1999-01-01

393

PDMS-based polyurethanes with MPEG grafts: synthesis, characterization and platelet adhesion study  

Microsoft Academic Search

Polyurethane (PU), based on poly(dimethyl siloxane) (PDMS) as a soft segment, with monomethoxy poly(ethylene glycol) (MPEG) grafted onto it, was synthesized as a new polymeric biomaterial for coating PDMS-based biomedical devices. Two different chain extenders, ethylene glycol (EG) and diethyl bis(hydroxymethyl) malonate (DBM), were used for the synthesis of PDMS-based PUs and then MPEG was grafted onto them by allophanate

Jae Hyung Park; Ki Dong Park; You Han Bae

1999-01-01

394

ATRP of Amphiphilic Graft Copolymers Based on PVDF and Their Use as Membrane Additives  

Microsoft Academic Search

The direct preparation of amphiphilic graft copolymers from commercial poly(vinylidene fluoride) (PVDF) using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary fluorinated site of PVDF facilitates grafting of the hydrophilic comonomer. Amphiphilic comb copolymer derivatives of PVDF having poly(methacrylic acid) side chains (PVDF-g- PMAA) and poly(oxyethylene methacrylate) side chains (PVDF-g-POEM) are prepared using this method.

J. F. Hester; P. Banerjee; Y.-Y. Won; A. Akthakul; M. H. Acar; A. M. Mayes

2002-01-01

395

Preparation of polystyrene grafted silica nanoparticles by two-steps UV induced reaction  

Microsoft Academic Search

Polystyrene grafted silica nanoparticles (PSSNs) were prepared by the followed two steps: methacryloxypropyl silica nanoparticles (MPSNs) were modified with the monomer-iniferter, 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) under UV irradiation. Then the VBDC modified silica nanoparticles (VBDCSNs) were used as iniferter for the surface-initiated (SI) controlled\\/“living” radical polymerization of styrene. A percentage of grafting (PG%) of 315.7% was achieved with a conversion of

Peng Liu; Zhixing Su

2004-01-01

396

Amphiphilic PPESK- graft-P(PEGMA) copolymer for surface modification of PPESK membranes  

Microsoft Academic Search

Amphiphilic graft copolymer consisting of poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly-(poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) side chains was synthesized by atomic transfer radical polymerization (ATRP). PPESK resin was beforehand chloromethylated, and the obtained chloromethylated PPESK (CMPPESK) containing benzyl chloride groups was used as macro-initiators to graft hydrophilic P(PEGMA) chains. The synthesized products were characterized by 1H NMR,

Li-Ping Zhu; You-Yi Xu; Han-Bang Dong; Zhuan Yi; Bao-Ku Zhu

2009-01-01

397

Poly( N-isopropylacrylamide) grafted poly(vinylidene fluoride) copolymers for temperature-sensitive membranes  

Microsoft Academic Search

Amphiphilic graft copolymers having poly(vinylidene fluoride) (PVDF) backbones and poly(N-isopropylacrylamide) (PNIPAAm) side chains were synthesized via ?-ray pre-irradiation induced graft polymerization in water phase suspension. No organic solvent was used in the synthesis process, which was harmless to environment. The resulting copolymers, PVDF-g-PNIPAAm, were characterized by nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA). It was showed that the PNIPAAm

Jing-Zhen Yu; Li-Ping Zhu; Bao-Ku Zhu; You-Yi Xu

2011-01-01

398

Halley's polymeric organic molecules  

SciTech Connect

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets. 31 refs.

Huebner, W.F.; Boice, D.C.; Korth, A.

1989-01-01

399

Molecularly imprinted polymeric membranes  

Microsoft Academic Search

Molecularly imprinted polymeric membranes have been emerged since 1990. Among various kinds of molecular imprinting studies, the application of molecular imprinting to membrane separation is still a novel investigation. In the present review paper, molecularly imprinted polymeric membranes are summarized and examined. The application of molecular imprinting to membrane separation shortly leads to high performance separation membranes.

Masakazu Yoshikawa

2001-01-01

400

Halley's polymeric organic molecules  

NASA Astrophysics Data System (ADS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

401

Halley's polymeric organic molecules  

NASA Technical Reports Server (NTRS)

The detection of polymeric organic compounds in the mass spectrum of Comet Halley obtained with the Positive Ion Cluster Composition analyzer on Giotto are examined. It is found that, in addition to polyoxymethylene, other polymers and complex molecules may exist in the comet. It is suggested that polymerized hydrogen cyanide may be a source for the observed CN and NH2 jets.

Huebner, W. F.; Boice, D. C.; Korth, A.

1989-01-01

402

Early Neural Grafts Transiently Reduce the Behavioral Effects of Radiation-Induced Fascia Dentata Granule Cell Hypoplasia. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

It is possible to produce selective hypoplasia of the hippocampal granule cells by X-irradiating the partially shielded rat brain. Specificity of damage is assured by conducting the radiation exposure when fascia dentata granule cells are mitotic, but adj...

G. A. Mickley J. L. Ferguson M. A. Mulvihill T. J. Nemeth

1991-01-01

403

Synthesis of polycaprolactone-grafted microfibrillated cellulose for use in novel bionanocomposites--influence of the graft length on the mechanical properties.  

PubMed

In the present work, microfibrillated cellulose (MFC) made from bleached sulfite softwood dissolving pulp was utilized to reinforce a poly(?-caprolactone) (PCL) biopolymer matrix. To improve the dispersibility of the hydrophilic MFC in the nonpolar matrix and the interfacial adhesion in the composite material, we covalently grafted the MFC with PCL via ring-opening polymerization (ROP) of ?-caprolactone (?-CL). To be able to investigate the effect of the PCL graft length on the mechanical properties of the composite material, we performed ROP to different molecular weights of the grafts. Bionanocomposites containing 0, 3, and 10 wt % MFC were prepared via hot pressing using both unmodified and PCL grafted MFC (MFC-g-PCL) as reinforcement. PCL grafting resulted in improved dispersion of the MFC in a nonpolar solvent and in the PCL matrix. The mechanical testing of the biocomposites showed an improvement in the mechanical properties for the PCL grafted MFC in comparison to ungrafted MFC. It was also shown that there was an impact on the mechanical properties with respect to the PCL graft lengths, and the strongest biocomposites were obtained after reinforcement with MFC grafted with the longest PCL graft length. PMID:21473594

Lönnberg, Hanna; Larsson, Karolina; Lindström, Tom; Hult, Anders; Malmström, Eva

2011-05-01

404

Plasma Graft Copolymerization of 4-Vinylpyridine on Dense and Porous SiLK for Electroless Plating of Copper and for Retardation of Copper Diffusion  

Microsoft Academic Search

c Chartered Semiconductor Manufacturing, Limited, Singapore 738406 Argon plasma-pretreated dense and porous SiLK films coated on Si100 wafers Si-SiLK wafers were subjected to plasma graft polymerization of 4-vinylpyridine 4VP. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results revealed that the pyridine functional groups of the plasma graft-polymerized 4VP pp4VP could be retained to a large extent under certain grow

Y. Q. Zhu; E. T. Kang; K. G. Neoh; T. Osipowicz; L. Chanc

2005-01-01

405

Chiral-nematic self-ordering of rodlike cellulose nanocrystals grafted with poly(styrene) in both thermotropic and lyotropic states  

Microsoft Academic Search

Graft copolymers of rodlike cellulose nanocrystals (CNC) with poly(styrene) (PSt) were synthesized through atom transfer radical polymerization (ATRP). The hydroxyl groups on CNC were esterified with 2-bromoisobutyrylbromide to yield 2-bromoisobutyryloxy groups, which were used to initiate the polymerization of poly(styrene). The graft copolymers were characterized by thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The

Jie Yi; Qunxing Xu; Xuefei Zhang; Hailiang Zhang

2008-01-01

406

Bioactive Polymer Grafting onto Titanium Alloy Surfaces for Improved Osteointegration  

PubMed Central

Bioactive polymers bearing sulfonate (styrene sodium sulfonate, NaSS) and carboxylate (methylacrylic acid, MA) groups were grafted onto Ti6Al4V alloy surfaces by a two-step procedure. The Ti alloy surfaces were first chemically oxidized in a piranha solution and then directly subjected to radical polymerization at 70°C in absence of oxygen. The grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the Toluidin blue colorimetric method. Toluidin blue results showed 1 to 5 ?g/cm2 of polymer was grafted onto the oxidized Ti surfaces. Grafting resulted in a decrease in the XPS Ti and O signals from the underlying Ti substrate and a corresponding increase in the XPS C and S signals from the polymer layer. The ToF-SIMS intensities of the S? and SO? ions correlated linearly with the XPS atomic percent S concentrations and the ToF-SIMS intensity of the TiO3H2? ion correlated linearly with the XPS atomic percent Ti concentration. Thus, the ToF-SIMS S?, SO? and TiO3H2? intensities can be used to quantify composition and amount of grafted polymer. ToF-SIMS also detected ions that were more characteristic of the polymer molecular structure (C6H4SO3? and C8H7SO3? from NaSS, C4H5O2? from MA), but the intensity of these peaks depended on the polymer thickness and composition. An in vitro cell culture test was carried out with human osteoblast-like cells to assess the influence of the grafted polymers on cell response. Cell adhesion after 30 min of incubation showed significant differences between the grafted and un-grafted surfaces. The NaSS grafted surfaces showed the highest degree of cell adhesion while the MA-NaSS grafted surfaces showed the lowest degree of cell adhesion. After 4 weeks in vivo in rabbit femoral bones bone was observed to be in direct contact with all implants. The percent of mineralized tissue around the implants was similar for NaSS grafted and non-grafted implants (59 and 57%). The MA-NaSS grafted implant exhibited a lower amount of mineralized tissue (47%).

Michiardi, Alexandra; Helary, Gerard; Nguyen, Phuong-Cac Thi; Gamble, Lara J.; Anagnostou, Fani; Castner, David G.; Migonney, Veronique

2013-01-01

407

Crystallization kinetics of maleic anhydride grafted polypropylene ionomers  

Microsoft Academic Search

Polypropylene (PP) was lightly maleated by solid-state graft polymerization and further neutralized to prepare semicrystalline ionomers, H+-, Na+-, Ca2+- and Mn2+-form maleated PP (mPP). The crystallization kinetics of pure PP and these ionomers have been investigated under isothermal and non-isothermal conditions. Under both conditions, the introduction of pendant groups along the PP chains increases the crystallization rate and does not

J. Yu; J. He

2000-01-01

408

Ruptured saphenous vein graft aneurysm after aortocoronary bypass grafting.  

PubMed

Computed tomography demonstrated a giant saphenous vein graft aneurysm that compressed the right atrium of a 72-year-old woman 20 years after undergoing coronary artery bypass grafting. Angiography revealed contrast medium leakage in the mid-portion of the graft aneurysm. Aneurysmectomy was performed without repeat grafting. Postoperative myocardial scintigraphy demonstrated no significant myocardial ischemia. The ischemic effect of non-revascularization should be considered preoperatively because of the difficulties with repeat grafting. PMID:22160413

Satsu, Takuma; Onoe, Masahiko; Miyashita, Naoya

2011-12-01

409

Ionic conductance behavior of polymeric electrolytes containing magnesium salts and their application to rechargeable batteries  

Microsoft Academic Search

Polymeric electrolytes consisting of oligo(ethylene oxide)-grafted polymethacrylate (PEO-PMA) matrix, linear polyether and magnesium salts have been prepared, and their electrochemical behavior as solid Mg2+ ion conductors has been examined. Thermal analyses showed that the obtained polymeric electrolytes are homogeneous and amorphous over a wide temperature range. The conductivity depended much on the kind of the dissolved magnesium salt. The highest

Nobuko Yoshimoto; Shin Yakushiji; Masashi Ishikawa; Masayuki Morita

2002-01-01

410

Grafting in Arabidopsis.  

PubMed

Grafting provides a simple way to generate chimeric plants with regions of different genotypes and thus to assess the cell autonomy of gene action. The technique of grafting has been widely used in other species, but in Arabidopsis, its small size makes the process rather more demanding. However, there are now several well-established grafting procedures available, which we described here, and their use has already contributed greatly to understanding of such processes as shoot branching control, flowering, disease resistance, and systemic silencing. PMID:24057364

Bainbridge, Katherine; Bennett, Tom; Crisp, Peter; Leyser, Ottoline; Turnbull, Colin

2014-01-01

411

Graft copolymers from cellulose: synthesis, characterization and evaluation.  

PubMed

Cellulose, a linear polysaccharide polymer with numerous glucose monosaccharide units is of enormous interest because of its applications in biosorption, biomedical, packaging, biofiltration and biocomposites. In this study, cellulose-graft-poly(butyl acrylate) copolymers were synthesized under microwave conditions. Effects of microwave radiation doses and different reaction parameters were optimized to get the optimum percentage of grafting. The dependence of optimum conditions for better physico-chemical properties of the cellulosic polymers was also determined. Fourier transform infrared spectroscopy (FT-IR) analysis was used to authenticate the chemical reaction taking place between cellulosic polymers and monomer. The thermogravimetric behavior of the raw and grafted cellulosic polymers was characterized by thermogravimetric analysis (TGA). The surface structure of the raw and grafted cellulosic polymers was analyzed through scanning electron microscopy (SEM). The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance. PMID:23769511

Thakur, Vijay Kumar; Thakur, Manju Kumari; Gupta, Raju Kumar

2013-08-14

412

Polymerization of Itaconic Acid.  

National Technical Information Service (NTIS)

Itaconic acid has various uses in chain copolymerization reactions, because of its two carboxylic groups and relatively good reactivity with different comonomers. As an unsaturated dicarboxylic acid it also has applications in grafting reactions and polyc...

J. Ahlgren

1990-01-01

413

Free Gingival Graft.  

National Technical Information Service (NTIS)

Shows how a split-flap and free gingival graft are used to correct gingival recession on a patient's two mandibular central incisors. Demonstrates achieving sufficient gain in gingival attachment to avoid muscle pull around these teeth.

1994-01-01

414

Interfacial Morphological Changes Caused by Grafting of Polymer Chains  

NASA Astrophysics Data System (ADS)

We follow the morphology of the interface between polystyrene (PS) and poly(styrene-r-maleic anhydride) (PSMA) at various normalized interfacial excesses z^*/Rg of graft copolymer formed by reaction between deuterated PS terminated with a benzyl amine group (dPS-NH_2) and (PSMA). For dPS-NH2 chains with polymerization indices N=250, 55 and 33, we find from forward recoil spectrometry that z^*/Rg values as large as 4, 9 and 40 respectively can be achieved. If these interfaces were planar, the tension of the graft copolymer interface should be negative. Using crossectional transmission electron microscopy we find however, as in the case of large z^*/Rg of segregating block copolymers, that the grafted interface is highly corrugated and extends over a region of about 300-400 nm. Scanning force microscopy shows that the wavelength of the corrugation is about 50 nm. Evidence for the formation of droplets of graft copolymer coated PSMA will also be presented. These interface morphologies seem to be the first step in the formation of a true polymeric microemulsion.

Jiao, J.; Kramer, E. J.; Möller, M.; de Vos, S.; Koning, C.

1997-03-01

415

Multiphase Polymeric Materials  

NSDL National Science Digital Library

Developed by a group of PhD students at the University of Southern Mississippi, the Multiphase Polymeric Materials Website presents both general information about composites and current research on multiphase polymeric materials, including information about blends, coatings, and nanocomposites. As the newest addition to Macrogalleria (described in the March 31, 1999 Scout Report for Science & Engineering), the Multiphase Polymeric Materials Website includes information on Composites in General, Composites, Characterization and Analysis, and Application. Most useful to researchers, the Application section introduces the relationship between polymer composites and component level electronics with examples such as PCB Construction, Encapsulation of Integrated Circuits, and Non-Conductive Adhesives.

416

PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'  

NASA Astrophysics Data System (ADS)

Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science (Symposium X of IUMRS-ICA2008) Toshiji Kanaya, Kohji Tashiro, Kazuo Sakura Keiji Tanaka, Sono Sasaki, Naoya Torikai, Moonhor Ree, Kookheon Char, Charles C Han, Atsushi Takahara This volume contains peer-reviewed invited and contributed papers that were presented in Symposium X 'Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Structure analyses of soft materials based on synchrotron radiation (SR) and neutron beam have been developed steadily. Small-angle scattering and wide-angle diffraction techniques clarified the higher-order structure as well as time dependence of structure development such as crystallization and microphase-separation. On the other hand, reflectivity, grazing-incidence scattering and diffraction techniques revealed the surface and interface structural features of soft materials. From the viewpoint of strong interests on the development of SR and neutron beam techniques for soft materials, the objective of this symposium is to provide an interdisciplinary forum for the discussion of recent advances in research, development, and applications of SR and neutron beams to soft matter science. In this symposium, 21 oral papers containing 16 invited papers and 14 poster papers from China, India, Korea, Taiwan, and Japan were presented during the three-day symposium. As a result of the review of poster and oral presentations of young scientists by symposium chairs, Dr Kummetha Raghunatha Reddy (Toyota Technological Institute) received the IUMRS-ICA 2008 Young Researcher Award. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. Organizing committee of Symposium (IUMRS-ICA 2008) Professor Toshiji Kanaya (Kyoto University) Professor Kohji Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y aimed to provide recent advances in polymer synthesis, self-assembling processes and morpholog

Takahara, Atsushi; Kawahara, Seiichi

2009-09-01

417

High stability of thermoresponsive polymer-brush-grafted silica beads as chromatography matrices.  

PubMed

Thermo-responsive chromatography matrices with three types of graft architecture were prepared, and their separation performance and stability for continuous use were investigated. Poly(N-isopropylacrylamide)(PIPAAm) hydrogel-modified silica beads were prepared by a radical polymerization through modified 4,4'-azobis(4-cyanovaleric acid) and N,N'-methylenebisacrylamide. Dense PIPAAm brush-grafted silica beads and dense poly(N-tert-Butylacrylamide (tBAAm)-b-IPAAm) brush-grafted silica beads were prepared through a surface-initiated atom transfer radical polymerization (ATRP) using CuCl/CuCl(2)/ Tris(2-(N,N-dimethylamino)ethyl)amine (Me(6)TREN) as an ATRP catalytic system and 2-propanol as a reaction solvent. Dense PIPAAm brush-grafted silica beads exhibited the highest separation performance because of their strong hydrophobic interaction between the densely grafted well-defined PIPAAm brush on silica-bead surfaces and analytes. Using an alkaline mobile phase, dense themoresponsive polymer brushes, especially having a hydrophobic basal layer, exhibited a high stability for continuous use, because polymer brush on the silica bead surfaces prevented the access of water to silica surface, leading to the hydrolysis of silica and cleavage of grafted polymers. Thus, the precisely modulating graft configuration of thermoresponsive polymers provided chromatography matrices with a high separation efficiency and stability for continuous use, resulting in elongating the longevity of chromatographic column. PMID:22452297

Nagase, Kenichi; Kobayashi, Jun; Kikuchi, Akihiko; Akiyama, Yoshikatsu; Kanazawa, Hideko; Okano, Teruo

2012-04-01

418

Surface modification of commercial cellulose acetate membranes using surface-initiated polymerization of 2-hydroxyethyl methacrylate to improve membrane surface biofouling resistance  

Microsoft Academic Search

To improve biofouling resistance, cellulose acetate (CA) reverse osmosis membranes were modified by reacting surface hydroxyl groups with an atom transfer radical polymerization (ATRP) initiator, 2-bromoisobutyryl bromide, followed by polymeric grafting of 2-hydroxyethyl methacrylate (pHEMA) using activators regenerated by electron transfer (ARGET) ATRP. Thermogravimetric analysis (TGA), atomic force microscopy (AFM) and water contact angle (WCA) measurements of pristine and modified

Clare H. Worthley; Kristina T. Constantopoulos; Milena Ginic-Markovic; Rachel J. Pillar; Janis G. Matisons; Stephen Clarke

2011-01-01

419

Rapid synthesis of graft copolymers from natural cellulose fibers.  

PubMed

Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its derivatives in a number of advanced applications, such as in paper, packaging, biosorption, and biomedical. In present communication, in an effort to develop a proficient way to rapidly synthesize poly(methyl acrylate)-graft-cellulose (PMA-g-cellulose) copolymers, rapid graft copolymerization synthesis was carried out under microwave conditions using ferrous ammonium sulfate-potassium per sulfate (FAS-KPS) as redox initiator. Different reaction parameters such as microwave radiation power, ratio of monomer, solvent and initiator concentrations were optimized to get the highest percentage of grafting. Grafting percentage was found to increase with increase in microwave power up to 70%, and maximum 36.73% grafting was obtained after optimization of all parameters. Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment. The grafted copolymers demonstrated increased chemical resistance, and higher thermal stability. PMID:23987417

Thakur, Vijay Kumar; Thakur, Manju Kumari; Gupta, Raju Kumar

2013-10-15

420

Kinetics of Silica Polymerization.  

National Technical Information Service (NTIS)

The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the tem...

A. Yee L. Tsao O. Weres

1980-01-01

421

Organometallic Polymeric Conductors.  

National Technical Information Service (NTIS)

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductiv...

W. J. Youngs

1997-01-01

422

Antimicrobial Polymeric Surfaces.  

National Technical Information Service (NTIS)

Bactericidal compositions are disclosed that comprise a polymeric compound immobilized on a material. Medical devices are also disclosed which comprise such a bactericidal composition. Methods are disclosed for covalently derivatizing the surfaces of comm...

J. C. Tiller C. J. Liao K. Lewis A. M. Klibanov

2005-01-01

423

Nickel adsorption by sodium polyacrylate-grafted activated carbon.  

PubMed

A novel sodium polyacrylate grafted activated carbon was produced by using gamma radiation to increase the number of functional groups on the surface. After irradiation the capacity for nickel adsorption was studied and found to have increased from 44.1 to 55.7 mg g(-1). X-ray absorption spectroscopy showed that the adsorbed nickel on activated carbon and irradiation-grafted activated carbon was coordinated with 6 oxygen atoms at 2.04-2.06 A. It is proposed that this grafting technique could be applied to other adsorbents to increase the efficiency of metal adsorption. PMID:19576692

Ewecharoen, A; Thiravetyan, P; Wendel, E; Bertagnolli, H

2009-11-15

424

Polymeric nitrogen. Revision 1  

Microsoft Academic Search

Ab initio local-density functional total-energy calculations indicate that a polymeric form should be the stable phase of nitrogen above â¼ 35 GPa, and that such a polyermic phase is likely to be both energetic and metastable at atmospheric pressure. These results also suggest that such a polymeric form of nitrogen may survive metastably at atompsheric pressure as an energetic, high-melting

C. Mailhiot; L. H. Yang; A. K. McMahan

1992-01-01

425

Nickel adsorption by sodium polyacrylate-grafted activated carbon  

Microsoft Academic Search

A novel sodium polyacrylate grafted activated carbon was produced by using gamma radiation to increase the number of functional groups on the surface. After irradiation the capacity for nickel adsorption was studied and found to have increased from 44.1 to 55.7mgg?1. X-ray absorption spectroscopy showed that the adsorbed nickel on activated carbon and irradiation-grafted activated carbon was coordinated with 6

A. Ewecharoen; P. Thiravetyan; E. Wendel; H. Bertagnolli

2009-01-01

426

Preparation and properties of plasma-initiated graft copolymerized membranes for blood plasma separation  

NASA Astrophysics Data System (ADS)

A hydrophilic composite membrane for blood plasma separation has been prepared by surface graft copolymerization initiated by low-temperature plasma (LTP). After short LTP pre-irradiation onto a microporous polypropylene (PP) membrane, N-N-dimethylacrylamide (DMAA) vapor was introduced for grafting. The PP membrane had a 0.45 ?m effective pore size and a 130 ?m thickness. The rate of DMAA grafting onto PP was very high, even in vapor-solid phase reaction under reduced pressure; DMAA 1 mm Hg (133Pa). The percentage of grafted poly-DMAA (PDMAA) reached 15% within 5 min post graft polymerization, and the membrane surface, including the interior surface of pores, became completely hydrophilic. There was no apparent change observed in the membrane morphology in the dry state after the PDMAA-grafted layer was formed. However, water flux significantly decreased, probably due to swelling of the PDMAA-grafted layer. With a grafting yield below 17%, the PDMAA-grafted PP (PP-g-PDMAA) membrane showed a good separation capability of plasma from whole blood. The PP-g-PDMAA membrane exhibited low complement activating potential, high sieving coefficient for plasma proteins and high blood compatibility. Decreases in adsorption of blood cells, plasma proteins, and other biomolecules may be the reason for the membrane performance.

Onishi, M.; Shimura, K.; Seita, Y.; Yamashita, S.; Takahashi, A.; Masuoka, T.

427

synthesis of novel four armed PE-PCL grafted superparamagnetic and biocompatible nanoparticles.  

PubMed

Novel biocompatible polymer immobilized superparamagnetic nanoparticles (MNP) are prepared by grafting four armed pentaerythritol poly(?-polycaprolactone) (PE-PCL) onto silane modified MNP. The MNPs are synthesized by hydrothermal process and its modification using (3-aminopropyl)trimethoxysilane (TMAS) coating is done by the sol-gel technique. The pentaerythritol (PE) initiated ring-opening polymerization (ROP) is carried out to prepare four armed PE-PCL. The reaction is shown to follow first order kinetics. The structure of PE-PCL is confirmed by NMR spectrum and MALDI-TOF analysis. The in situ grafting of PE-PCL onto modified MNP has been carried out by using 4,4'-methylenediphenyl diisocyanate (MDI) as an intermediate linker. The grafting density as determined by TGA analysis has been found to be significantly higher than previously reported linear PCL grafted MNPs in the literature. This leads to uniform dispersion of grafted MNPs which still is a challenging task in contemporary research. The effective dispersion of MNP into PE-PCL matrix is analyzed by HRTEM. The saturation magnetization of the PE-PCL grafted MNPs is significantly high and this can be tailored further by varying the grafting density. The biocompatibility of polymer grafted nanoparticles is confirmed by MTT assay using HeLa cell line. The superparamagnetic and biocompatible novel PE-PCL grafted MNP so prepared would have manifold potential applications including in therapy and targeted drug delivery. PMID:24041315

Panja, Sudipta; Saha, Biswajit; Ghosh, S K; Chattopadhyay, Santanu

2013-10-01

428

Long-term hip simulator testing of the artificial hip joint bearing surface grafted with biocompatible phospholipid polymer.  

PubMed

To prevent periprosthetic osteolysis and subsequent aseptic loosening of artificial hip joints, we recently developed a novel acetabular highly cross-linked polyethylene (CLPE) liner with graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) on its surface. We investigated the wear resistance of the poly(MPC) (PMPC)-grafted CLPE liner during 20 million cycles in a hip joint simulator. We extended the simulator test of one liner to 70 million cycles to investigate the long-term durability of the grafting. Gravimetric, surface, and wear particle analyses revealed that PMPC grafting onto the CLPE liner surface markedly decreased the production of wear particles and showed that the effect of PMPC grafting was maintained through 70 million cycles. We believe that PMPC grafting can significantly improve the wear resistance of artificial hip joints. PMID:24249706

Moro, Toru; Takatori, Yoshio; Kyomoto, Masayuki; Ishihara, Kazuhiko; Hashimoto, Masami; Ito, Hideya; Tanaka, Takeyuki; Oshima, Hirofumi; Tanaka, Shigeyuki; Kawaguchi, Hiroshi

2014-03-01

429

Controlled synthesis of photochromic polymer brushes by atom transfer radical polymerization  

Microsoft Academic Search

This work reports on the grafting of methyl methacrylate polymer brushes containing spirobenzopyran pendant groups from flat silica surfaces and colloidal particles utilizing atom transfer radical polymerization (ATRP). The reaction conditions were optimized with respect to the kind of surface bound initiator, the type of halide and ligand used in the catalytic complex, the presence\\/absence of untethered initiator, and solvent

Marcin Piech; Nelson Simmons Bell; Timothy Michael Long

2005-01-01

430

Surface modification of polymeric biomaterials with poly(ethylene oxide), albumin, and heparin for reduced thrombogenicity  

Microsoft Academic Search

Appropriate surface modification has significantly improved the blood compatibility of polymeric biomaterials. This article reviews methods of surface modification with water-soluble polymers, such as polyethylene oxide (PEO), albumin, and heparin. PEO is a synthetic, neutral, watersoluble polymer, while albumin and heparin are a natural globular protein and an anionic polysaccharide, respectively. When grafted onto the surface, all three macromolecules share

Mansoor Amiji

1993-01-01

431

Halamine polymers: 2. Preparation of new triazine-diones biocidal polymers by grafting polymerisation  

Microsoft Academic Search

New N-halamine polymeric compounds were prepared by reacting cyanuric acid and polyacrylonitrile. Grafting of acrylonitrile monomer onto cotton linters was carried out and the product was reacted with cyanuric acid and finally was chlorinated. Cyanoethylation of polyvinyl alcohol was performed using acrylonitrile monomer to give polyvinylcyanoethyl ether, which, in turn, was reacted with cyanuric acid. The biological activity of the

A. M. El-Masry; H. Y. Moustafa; A. I. Ahmed; A. F. Shaaban

2004-01-01

432

Hydrophobic magnesium hydroxide nanoparticles via oleic acid and poly(methyl methacrylate)-grafting surface modification  

Microsoft Academic Search

Hydrophobic magnesium hydroxide nanoparticles were obtained by means of grafting poly(methyl methacrylate) (PMMA) onto the surface of nanoparticles after oleic acid (OA) modification. The introduction of functional double bonds was firstly conducted on the surface of nanoparticles by OA modification, followed by dispersion polymerization on the particles surface in ethanol solution using methyl methacrylate (MMA) as monomer, azoisobutyronitrile (AIBN) as

Hong Yan; Xue-hu Zhang; Li-qiao Wei; Xu-guang Liu; Bing-she Xu

2009-01-01

433

Diffusion of Small Molecules in Radiation Damaged PMMA.  

National Technical Information Service (NTIS)

Ultraviolet irradiation of poly(methylmethacrylate), PMMA, creates radicals which can initiate polymerization of acrylic acid to form block and/or graft copolymer with solubility different from that of PMMA. Selective development of modified PMMA produces...

J. A. Moore S. Y. Kim

1990-01-01

434

Adhesive cell cultivation on polymer particle having grafted epoxy polymer chain.  

PubMed

In this study, we synthesized a new cell immobilization support having poly(glycidyl methacrylate) as a graft polymer chain and used this support for cell cultivation. Base polymer particle was synthesized by suspension polymerization and epoxy polymer chain was extended from particle surface on graft polymerization. Produced polymer particles had broad particle size distribution ranging from 20 to 1000 ?m and the degree of polymerization of grafted polymer chain was ranged from 500 to 1000. The effects of various factors, such as grafted polymer chain length and its surface density, composition of base polymer network and graft polymer chain, on the cell growth of murine fibroblast cell line (MS-5 cell) on polymer particle were studied. This polymer particle could cultivate not only fibroblast cell line but also epidermal cell line (HeLa cell), osteoblast cell line (MC3T3E1 cell), and chondrocyte cell line (ch-8 cell) on its surface. Growth rate is almost the same as that of cells using poly(styrene) tissue culture dish. To apply this cell cultivation system for examination of cell co-culture, HeLa cell immobilized on 100 ?m of polymer particle was successfully co-cultured with MS-5 cell immobilized on 300 ?m of polymer particle for four weeks. PMID:21349566

Yasuda, Masahiro; Kunieda, Hiroshi; Ono, Kentaro; Ogino, Hiroyasu; Iwasaki, Tomohiro; Hiramoto, Masaki; Glomm, Wilhelm Robert; Hirabayashi, Yukio; Aizawa, Shin

2011-04-01